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ASTRONOMICAL CURIOSITIES

FACTS AND FALLACIES

ASTRONOMICAL
CURIOSITIES

FACTS AND FALLACIES

J. ELLARD GORE

MEMBER OF THE ROYAL IRISH ACADEMY
FELLOW OK THE ROYAL ASTRONOMICAL SOCIETY

CORRESPONDING MEMBER OF THE ROYAL ASTRONOMICAL SOCIETY OF CANADA

ETC.

AUTHOR OF "ASTRONOMICAL ESSAYS," "STUDIES IN ASTRONOMY"
"THE VISIBLE UNIVERSE," ETC.

- or THE
UNIVERSITY

•lfe«

LONDON
CHATTO & WINDUS

1909

PRINTED BY

WILLIAM CLOWES AND SONS, LIMITED
LONDON AND BECCLES

PREFACE

THE curious facts, fallacies, and paradoxes con-
tained in the following pages have been collected
from various sources. Most of the information
given will not, I think, be found in popular works
on astronomy, and will, it is hoped, prove of
interest to the general reader.

J. E. G.

September, 1900.

201609

CONTENTS

CHAPTER P1GB

I. THE SUN ... ... ... ... ... 1

II. MERCURY ... ... ... ... 10

in. VENUS ... ... ... ... ... 17

IV. THE EARTH ... ... ... ... 32

V. THE MOON ... ... ... ... 48

VI. MARS ... ... ... ... 59

Vn. THE MINOR PLANETS ... ... ... 68

vm. JUPITER ... ... ... ... 74

IX. SATURN ... ... ... ... ... 84

X. URANUS AND NEPTUNE ... ... ... 91

XI. COMETS ... ... ... ... ... 97

XII. METEORS ... ... ... ... 117

XIII, THE ZODIACAL LIGHT AND GEGEXSCHKIN ... 127

XIV. THE STARS ... ... ... ... 135

XV. DOUBLE AND BINARY STARS ... ... ... 160

XVI. VARIABLE STARS ... ... ... 170

XVII. NEBUUE AND CLUSTERS ... ... ... 191

XVIII. HISTORICAL ... ... ... ... 217

XIX. THE CONSTELLATIONS ... ... ... 239

XX. THE VISIBLE UNIVERSE ... ... ... 313

XXI. GENERAL ... ... ,.* ... ... 329

INDEX .,, 359

ILLUSTRATIONS

PAGE

AL-SUFI'S "EARTHEN JAR" ... .*• 247

AL-SUFI'S "FISHES" IN ANDROMEDA ... ... 249

0? THE

UNIVERSITY

ASTRONOMICAL
CURIOSITIES

CHAPTER I

The Sun

SOME observations recently made by Prof. W.
H. Pickering in Jamaica, make the value of
sunlight 540,000 times that of moonlight.
This makes the sun's " stellar magnitude " minus
2()'83, and that of moonlight minus 12'5. Prof.
Pickering finds that the light of the full moon is
equal to 100,000 stars of zero magnitude. He finds
that the moon's " albedo " is about 0-0909 ; or in
other words, the moon reflects about one-tenth of
the light which falls on it from the sun. He also
finds that the light of the full moon is about
twelve times the light of the half moon : a curious
and rather unexpected result.

M. C. Fabry found that during the total eclipse
of the sun on August 30, 1905; the light of the
corona at a distance of five minutes of arc from the
sun's limit, and in the vicinity of the sun's equator,
was about 720 candle-power. Comparing this

2 ASTRONOMICAL CURIOSITIES

with the intrinsic light of the full moon (2600
candle-power) we have the ratio of 0*28 to 1.
He finds that the light of the sun in the zenith,
and at its mean distance from the earth, is 100,000
times greater than the light of a " decimal candle "
placed at a distance of one metre from the eye.1
He also finds that sunlight is equal to 60,000
million times the light of Vega. This would make
the sun's " stellar magnitude " minus 26*7, which
does not differ much from Prof. Pickering's result,
given above, and is probably not far from the truth.

From experiments made in 1906 at Moscow,
Prof. Ceraski found that the light of the sun's
limb is only 31*4 to 38'4 times brighter than the
illumination of the earth's atmosphere very near
the limb. This is a very unexpected result ; and
considering the comparative faintness of the sun's
corona during a total eclipse, it is not surprising
that all attempts to photograph it without an
eclipse have hitherto failed.2

From Paschen's investigations on the heat of
the sun's surface, he finds a * result of 5961°
(absolute), " assuming that the sun is a perfectly
black body."3 Schuster finds that "There is a
stratum near the sun's surface having an average
temperature of approximately 5500° C., to which
about 0*3 of the sun's radiation is due. The

1 Comptes Rendus, 1903, December 7.

• Nature, April 11, 1907.

3 Astrophysical Journal, vol. 19 (1904), p. 39.

THE SUN 3

remaining portion of the radiation has an
intensity equal to that due to a black body
having a temperature of about 6700° C." The
above results agree fairly well with those found by
the late Dr. W. E. Wilson.1 The assumption of
the sun being " a black body " seems a curious
paradox ; but the simple meaning of the state-
ment is that the sun is assumed to act as a
radiator as if it vvere a perfectly black body heated
to the high temperature given above.

According to Prof. Langley, the sun's photo-
sphere is 5000 times brighter than the molten
metal in a " Bessemer converter." 2

Observations of the sun even with small tele-
scopes and protected by dark glasses are very
dangerous to the eyesight. Galileo blinded him-
self in this way ; Sir William Herschel lost one of
his eyes ; and some modern observers have also
suffered. The present writer had a narrow escape
from permanent injury while observing the transit
of Venus, in 1874, in India, the dark screen before
the eyepiece of a 3-inch telescope having blistered
— that is, partially fused during the observation.
Mr. Cooper, Markree Castle, Ireland, in observing
the sun, used a " drum " of alum water and dark
spectacles, and found this sufficient protection
against the glare in using his large refracting
telescope of 13%3-inches aperture.

1 Astrophysical Journal, vol. 21 (1905), p. 260.

2 Knowledge, July, 1902, p. 132.

4 ASTRONOMICAL CURIOSITIES

Prof. Mitchell, of Columbia University (U.S.A.),
finds that lines due to the recently discovered
atmospherical gases argon and neon are present in
the spectrum of the sun's chromosphere. The
evidence for the existence of krypton and xenon
is, however, inconclusive. Prof. Mitchell suggests
that these gases may possibly have reached the
earth's atmosphere from the sun. This would
agree with the theory advanced by Arrhenius
that " ionised particles are constantly being
repulsed by the pressure of light, and thus
journey from one sun to another."1

Prof. Young in 1870, and Dr. Kreusler in June,
1904, observed the helium line D3 as a dark line
" in the spectrum of the region about a sun-spot." a
This famous line, from which helium was originally
discovered in the sun, and by which it was long
afterwards detected in terrestrial minerals, usually
appears as a bright line in the spectrum of the
solar chromosphere and "prominences." It has
also been seen dark by Mr. Buss in sun-spot
regions.3

The discovery of sun-spots was claimed by
Hariotte, in 1610, and by Galileo, Fabricius, and
Schemer, in 1611. The latter wrote 800 pages on
them, and thought they were small planets revolv-
ing round the sun ! This idea was also held by
Tarde, who called them Astra Borbonia, and by

* Nature, April 30, 1903. 2 Ibid., May 18, 1905.

3 Ibid., May 18, 1905.

THE SUN 5

C. Malapert, who termed them Sydera Austricea.
But they seem to have been noticed by the
ancients.

Although in modern times there has been no
extraordinary development of sun-spots at the
epoch of maximum, it is not altogether impossible
that in former times these spots may have
occasionally increased to such an extent, both
in number and size, as to have perceptibly
darkened the sun's light. A more probable
explanation of recorded sun-darkenings seems,
however, to be the passing of a meteoric or
nebulous cloud between the sun and the earth.
A remarkable instance of sun-darkening recorded
in Europe occurred on May 22, 1870, when the
sun's light was observed to be considerably
reduced in a cloudless sky in the west of Ireland,
by the late John Birmingham ; at Greenwich on
the 23rd ; and on the same date, but at a later
hour, in North-Eastern France — " a progressive
manifestation," Mr. Birmingham says, " that seems
to accord well with the hypothesis of moving
nebulous matter." A similar phenomenon was
observed in New England (U.S.A.), on September
6, 1881.

One of the largest spots ever seen on the sun was
observed in June, 1843. It remained visible for
seven or eight days. According to Schwabe — the
discoverer of the sun-spot period — its diameter
was 74,000 miles, so that its area was many times

6 ASTRONOMICAL CURIOSITIES

that of the earth's surface. The most curious
thing about this spot was that it appeared near a
mjnwium of the sun-spot cycle ! and was there-
fore rather an anomalous phenomenon. It was
suggested by the late Daniel Kirkwood that this
great spot was caiised by the fall of meteoric
matter into the sun ; and that it had possibly
some connection with the great comet of 1843,
which approached the sun nearer than any other
recorded comet, its distance from the sun at
perihelion being about 65,000 miles, or less than
one-third of the moon's distance from the earth.
This near approach of the comet to the sun
occurred about three months before the appear-
ance of the great sun-spot ; and it seems probable
that the spot was caused by the downfall of a
large meteorite travelling in the wake of the
comet.1 The connection between comets and
meteors is well known.

The so-called blackness of sun-spots is merely
relative. They are really very bright. The most
brilliant light which can be produced artificially
looks like a black spot when projected on the
sun's disc.

According to Sir Robert Ball a pound of coal
striking a body with a velocity of five miles a
second would develop as much heat as it would
produce by its combustion. A body falling into
the sun from infinity would have a velocity of
1 Nature, June 29, 1871.

THE SUN 7

450 miles a second when it reached the sun's
surface. Now as the momentum varies as the
square of the velocity we have a pound of coal

developing 902( = ^-Y, or 8,100 times as much

heat as would be produced by its combustion.
If the sun were formed of coal it would be con-
sumed in about 3000 years. Hence it follows that
the contraction of the sun's substance from
infinity would produce a supply of heat for
3000 x 8100, or 24,300,000 years.

The late Mr. Proctor and Prof. Young believed
" that the contraction theory of the sun's heat is
the true and only available theory.'* The theory
is, of course, a sound one; but it may now be
supplemented by supposing the sun to contain a
certain small amount of radium. This would
bring physics and geology into harmony. Proctor
thought the " sun's real globe is very much smaller
than the globe we see. In other words the process
of contraction has gone on further than, judging
from the sun's apparent size, we should suppose it
to have done, and therefore represents more sun
work " done in past ages.

With reference to the suggestion, recently
made, that a portion, at least, of the sun's heat
may be due to radium, and the experiments which
have been made with negative results, Mr. R. T.
Strutt — the eminent physicist — has made some
calculations on the subject and says, " even if all

8 ASTRONOMICAL CURIOSITIES

the sun's heat were due to radium, there does not
appear to be the smallest possibility that the
Becquerel radiation from it could ever be detected
at the earth's surface." l

The eminent Swedish physicist Arrhenius,
while admitting that a large proportion of the
sun's heat is due to contraction, considers that it
is probably the chemical processes going on in
the sun, and not the contraction which constitiite
the chief source of the solar heat.2

As the centre of gravity of the sun and Jupiter
lies at a distance of about 460,000 miles from the
sun's centre, and the sun's radius is only 433,000
miles, it follows that the centre of gravity of the
sun and planet is about 27,000 miles outside the
sun's surface. The attractions of the other
planets perpetually change the position of the
centre of gravity of the solar system; but in
some books on astronomy it is erroneously
stated that the centre of gravity of the system
is always within the sun's surface. If all the
planets lay on the same side of the sun at
the same time (as might possibly happen), then
the centre of gravity of the whole system would
lie considerably more than 27,000 miles outside the
sun's surface.

With reference to the sun's great size, Carl
Snyder has well said, " It was as if in Vulcan's

1 Nature, October 15, 1903.

2 The Life of the Universe (1909). vol. ii. p. 209.

THE SUN 9

smithy the gods had moulded one giant ball, and
the planets were but bits and small shot which
had spattered off as the glowing ingot was cast
and set in space. Little man on a little part of a
little earth — a minor planet, a million of which
might be tumbled into the shell of the central
sun — was growing very small ; his wars, the con-
vulsions of a state, were losing consequence.
Human endeavour, human ambitions could now
scarce possess the significance they had when men
could regard the earth as the central fact of the
universe." '

With reference to the late Prof. C. A. Young
(U.S.A.) — a great authority on the sun — an
American writer has written the following
lines : —

" The destined course of whirling worlds to trace,
To plot the highways of the universe,
And hear the morning stars their song rehoarse,
And find the wandering comet in his place ;
This is the triumph written in his face,
And in the gleaming eye that read the sun
Like open book, and from the spectrum won
The secrets of immeasurable space." 2

1 The World Machine, p. 234.

- Quoted in The Observatory, March 1908, p. 125.

CHAPTER II

Mercury

A the elongation of Mercury from the sun
seldom exceeds 18°, it is a difficult object,
at least in this country, to see without a
telescope. As the poet says, the planet —

" Can scarce be caught by philosophic eye
Lost in the near effulgence of its blaze."

Tycho Brahe, however, records several obser-
vations of Mercury with the unaided vision in
Denmark.

It can be occasionally caught with the naked
eye in this country after sunset, when it is
favourably placed for observation, and I have so
seen it several times in Ireland. On February 19,
1888, I found it very visible in strong twilight near
the western horizon, and apparently brighter than
an average star of the first magnitude would be in
the same position. In the clear air of the Punjab
sky I observed Mercury on November 24-29, 1872,
near the western horizon after sunset. Its appear-
ance was that of a reddish star of the first magni-
tude. On November 29 I compared its brilliancy

MERCURY 11

with that of Saturn, which was some distance
above it, and making allowance for the glare near
the horizon in which Mercury was immersed, its
brightness appeared to me to be quite equal to
that of Saturn. In June, 1874, I found it equal to
Aldebaran, and of very much the same colour.
Mr. W. F. Denning, the famous observer of
meteors, states that he observed Mercury with the
naked eye about 150 times during the years 1868 to
1905.1

He found that the duration of visibility after
sunset is about lh 40m when seen in March, lh 30m in
April, and lh 20m in May. He thinks that the
planet is, at its brightest, " certainly much
brighter than a first magnitude star.2 In February,
1868, he found that its brightness rivalled that of
Jupiter, then only 2° or 3° distant. In November,
1882, it seemed brighter than Sirius. In 1876 it
was more striking than Mars, but the latter was
then " faint and at a considerable distance from
the earth."

In 1878, when Mercury and Venus were in the
same field of view of a telescope, Nasmyth found
that the surface brightness (or " intrinsic bright-
ness," as it is called) of Venus was at least twice
as great as that of Mercury ; and Zollner found
that from a photometric point of view the surface
of Mercury is comparable with that of the moon.

1 The Observatory, September, 190C.

2 Nature, March 1, 1900.

12 ASTRONOMICAL CURIOSITIES

With reference to the difficulty of seeing
Mercury, owing to its proximity to the sun,
Admiral Smyth says, " Although Mercury is never
in opposition to the earth, he was, when in the
house of Mars, always viewed by astrologers as
a most malignant planet, and one full of evil
influences. The sages stigmatized him as a false
deceitful star (sidus dolosum), the eternal torment
of astronomers, eluding them as much as terres-
trial mercury did the alchemists ; and Goad, who
in 1686 published a whole folio volume full of
astro-meteorological aphorisms, unveiling the
choicest secrets of nature, contemptuously calls
Mercury a * squinting lacquey of the sun, who
seldom shows his head in these parts, as if he was
in debt.' His extreme mobility is so striking that
chemists adopted his symbol to "denote quick-
silver." 1

Prof. W. H. Pickering thinks that the shortness
of the cusps (or " horns ") of Mercury's disc
indicates that the planet's atmosphere is of small
density — even rarer than that of Mars.

The diameter of Mercury is usually stated at
about 3000 miles ; but a long series of measures
made by Prof. See in the year 1901 make the real
diameter about 2702 miles. This would make
the planet smaller than some of the satellites of the
large planets, probably smaller than satellites III.
and IV. of Jupiter, less than Saturn's satellite
1 Cycle of Celestial Objects, p. 96.

MERCURY 13

Titan, and possibly inferior in size to the satellite
of Neptune. Prof. Pickering thinks that the
density of Mercury is about 3 (water = 1). Dr.
See's observations show " no noticeable falling off
in the brightness of Mercury near the limb."
There is therefore no evidence of any kind of
atmospheric absorption in Mercury, and the
observer " gets the impression that the physical
condition of the planet is very similar to that of
our moon." l '

Schroter (1780-1815) observed markings on
Mercury, from which he inferred that the planet's
surface was mountainous, and one of these
mountains he estimated at about 11 miles in
height ! 2 But this seems very doubtful.

To account for the observed irregularities in the
motion of Mercury in its orbit, Prof. Newcomb
thinks it possible that there may exist a ring or
zone of " asteroids " a little " outside the orbit of
Mercury" and having a combined mass of " one -
fiftieth to oiie-three-hundredth of the mass of
Venus, according to its distance from Mercury."
Prof. Newcomb, however, considers that the
existence of such a ring is extremely improbable,
and regards it " more as a curiosity than a
reality." 3

M. Leo Brenner thinks that he has seen the

1 Ast. Naeh. No. 3737.

2 Observatory, September, 1906.

3 Nature, November 29 and December 20, 1894.

U ASTRONOMICAL CURIOSITIES

dark side of Mercury, in the same way that the
dark side of Venus has been seen by many
observers. In the case of Mercury the dark side
appeared darker than the background of the sky.
Perhaps this may be due to its being projected
on the zodiacal light, or outer envelope of the

sun.1

Mercury is said to have been occulted by
Venus in the year 1737.3 But whether this was
an actual occultation, or merely a near approach
does not seem to be certain.

The first transit of Mercury across the sun's
disc was observed by Gassendi on November 6,
1631, and Halley observed one on November 7,
1677, when in the island of St. Helena.

Seen from Mercury, Venus would appear
brighter than even we see it, and as it would be
at its brightest when in opposition to the sun,
and seen on a dark sky with a full face, it must
present a magnificent appearance' in the midnight
sky of Mercury. The earth will also form a
brilliant object, and the moon would be distinctly
visible. The other planets would appear very
much as they do to us, but with somewhat less
brilliancy owing to their greater distance.

As the existence of an intra-Mercurial planet
(that is a planet revolving round the sun within
the orbit of Mercury) seems now to be very

1 Bulletin, Ast. Soc. de France, July, 1898.

2 Observatory, vol. 8 (1885), pp. 300-7.

MERCURY 15

improbable, Prof. Perrine suggests that possibly
" the finely divided matter which produces the
zodiacal light when considered in the aggregate
may be sufficient to cause the perturbations
the orbit of Mercury." l Prof. Newcomb, how
ever, questions the exact accuracy of Newton's
law, and seems to adopt Hall's hypothesis that
gravity does not act exactly as the inverse square
of the distance, and that the exponent of the
distance is not 2, but 2'0000001574.2

Voltaire said, " If Newton had been in Portugal,
and any Dominican had discovered a heresy in his
inverse ratio of the squares of the distances, he
would without hesitation have been clothed in a
san benito, and burnt as a sacrifice to God at an
auto da /<£." 3

An occultation of Mercury by Venus was
observed with a telescope on May 17, 1737.4

May transits of Mercury across the sun's disc
will occur in the years 1924, 1957, and 1970 ; and
November transits in the years 1914, 1927, and
1940.5

From measurements of the disc of Mercury
during the last transit, M. R. Jonckheere concludes
that the polar diameter of the planet is greater

1 Nature, October 30, 1902.

2 Charles Lane Poor, TJie Solar System, p. 170.

3 Smyth, Celestial Cycle, p. 60.

4 Denning, Telescopic itfbrk for Starlight Evenings, p. 225.

5 The Observatory, 1894. p. 395.

16 ASTRONOMICAL CURIOSITIES

than the equatorial! His result, which is very
curious, if true, seems to be supported by the
observations of other observers.1

The rotation period of Mercury, or the length
of its day, seems to be still in doubt. From a
series of observations made in the years 1890 to
1909, Mr. John McHarg finds a period of 1-0121162
day, or ld Oh 17m 26S'8. He thinks that "the
planet possesses a considerable atmosphere not
so clear as that of Mars " ; that " its axis is very
considerably tilted " ; and that it " has fairly
large sheets of water." 2

1 Ast. Nach. 4333, quoted in Nature, July 1, 1009, p. 20.

2 English Mechanic, July 23, 1901).

CHAPTER III

Venus

VENUS was naturally — owing to its bright-
ness— the first of the planets known to
the ancients. It is mentioned by Hesiod,
Homer, Virgil, Martial, and Pliny ; and Isaiah's
remark about "Lucifer, son of the morning"
(Isaiah xiv. 12) probably refers to Venus as a
" morning star." An observation of Venus is
found on the Nineveh tablets of date B.C. 684.
It was observed in daylight by Halley in July,
1716.

In very ancient times Venus, when a morning
star, was called Phosphorus or Lucifer, and when
an evening star Hesperus ; but, according to Sir
G. C. Lewis, the identity of the two objects was
known so far back as 540 B.C.

When Venus is at its greatest brilliancy, and
appears as a morning star about Christmas time
(which occurred in 1887, and again in 1889), it has
been mistaken by the public for a return of the
" Star of Bethlehem." l But whatever " the star
1 Nature, December 22, 1892.

18 ASTRONOMICAL CURIOSITIES

of the Magi" was it certainly was not Venus.
It, seems, indeed absurd to suppose that " the wise
men " of the East should have mistaken a familiar
object like Venus for a strange apparition. There
seems to be nothing whatever in the Bible to lead
us to expect that the star of Bethlehem will
reappear.

Mr. J. H. Stockwell has suggested that the
" Star of Bethlehem " may perhaps be explained
by a conjunction of the planets Venus and
Jupiter which occurred on May 8, B.C. 6, which
was two years before the death of Herod. From
this it would follow that the Crucifixion took
place on April 3, A.D. 33. But it seems very
doubtful that the phenomenon recorded in the
Bible refers to any conjunction of planets.

Chacornac found the intrinsic brightness of
Venus to be ten times greater than the most
luminous parts of the moon.1 But this estimate
is probably too high.

When at its brightest, the planet is visible in
broad daylight to good eyesight, if its exact
position in the sky is known. In the clear air of
Cambridge (U.S.A.) it is said to be possible to see
it in this way in all parts of its orbit, except
when the planet is within 10° of the sun.2 Mr.
A. Cameron, of Yarmouth, Nova Scotia, has,
however, seen Venus with the naked eye three

1 Celestial Objects> vol. i. p. 52, footnote.

2 Ibid., p. 54.

VENUS 19

days before conjunction when the planet was
only 61° from the sun.1 This seems a remarkable
observation, and shows that the observer's eye-
sight must have been very keen. In a private
letter dated October 22, 1888, the late Rev. S. J.
Johnson informed the present writer that he saw
Venus with the naked eye only four days before
conjunction with the sun in February, 1878, and
February, 1886.

The crescent shape of Venus is said to have
been seen with the naked eye by Theodore Parker
in America when he was only 12 years old. Other-
observers have stated the same thing ; but the
possibility of such an observation has been much
disputed in recent years.

In the Chinese Annals some records are given
of Venus having been seen in the Pleiades. On
March 16, A.D. 845, it is said that " Venus eclipsed
the Pleiades.'* This means, of course, that the
cluster was apparently effaced by the brilliant light
of the planet. Computing backwards for the above
date, Hind found that on the evening of March 16,
845, Venus was situated near the star Electra ;
and on the following evening the planet passed
close to Maia ; thus showing the accuracy of
the Chinese record. Another " eclipse " of the
Pleiades by Venus is recorded in the same annals
as having occurred 011 March 10, A.D. 1002.2 H

1 Astronomy and Astrophysics, 1892, p. 618.
- Nature, August 7, 1879.

20 ASTRONOMICAL CURIOSITIES

When Venus is in the crescent phase, that is
near " Inferior conjunction " with the sun, it will
be noticed, even by a casual observer, that the
crescent is not of the same shape as that of the
crescent moon. The horns or "cusps" of
the planetary crescent are more prolonged than
in the case of the moon, and extend beyond the
hemisphere. This appearance is caused by refrac-
tion of the sun's light through the planetary
atmosphere, and is, in fact, a certain proof that
Venus has an atmosphere similar to that of the
earth. Observations further show that this
atmosphere is denser than ours.

Seen from Venus, the earth and moon, when
in opposition, must present a splendid spectacle.
I find that the earth would shine as a star about
half as bright again as Venus at her brightest
appears to us, and the moon about equal in
brightness to Sirius! the two forming a superb
" naked eye double star " — perhaps the finest
sight of its kind in the solar system.1

Some of the earlier observers, such as La Hire,
Fontana, Cassini, and Schroter, thought they
saw evidence of mountains on Venus. Schroter
estimated some of these to be 27 or 28 miles in
height! but this seems very doubtful. Sir
William Herschel severely attacked these supposed
discoveries. Schroter defended himself, and was
supported by Beer and Madler, the famous
1 The World of Space, p. 56.

VENUS 21

lunar observers. Several modern observers
seem to confirm Schroter's conclusions ; but very
little is really known about the topography of
Venus.

The well-known French astronomer Trouvelot —
a most excellent observer — saw white spots on
Venus similar to those on Mars. These were well
seen and quite brilliant in July and August, 1876,
and in February and November, 1877. The
observations seem to show that these spots do
not (unlike Mars) increase and decrease with the
planet's seasons. These white spots had been
previously noticed by former observers, including
Biaiichini, Derham, Gruithuisen, and La Hire;
but these early observers do not seem to have
considered them as snow caps, like those of Mars.
Trouvelot was led by his own observations to
conclude that the period of rotation of Venus
is short, and the best result he obtained was
23h 49m 28s. This does not differ much from the
results previously found by De Vico, Fritsch, and
Schroter.1

A white spot near the planet's south pole was
seen on several occasions by H. C. Russell in May
and June, 1876.2

Photographs of Venus taken 011 March 18 and
April 29, 1908, by M. Quenisset at the Observatory
of Juvissy, France, show a white polar spot. The

1 Nature, September 15, 1892.

2 Olservatory, 1880, p. 574.

22 ASTRONOMICAL CURIOSITIES

spot was also seen at the same observatory by
M. A. Benoit on May 20, 1903.

The controversy on the period of rotation of
Venus, or the length of its day, is a very curious
one and has not yet been decided. Many good
observers assert confidently that it is short (about
24 hours); while others affirm with equal con-
fidence that it is long (about 225 days, the period
of the planet's revolution round the sun). Among
the observers who favour the short period of
rotation are : D. Cassini (1667), J. Cassini (1730),
Schroter (1788-93), Madler (1836), De Vico (1840?)
Trouvelot (1871-79), Flammarion, Leo Brenner,
Stanley Williams, and J. McHarg; and among
those who support the long period are : Bianchini
(1727), Schiaparelli, Cerulli, Tacchini, Mascari,
and Lowell. Some recent spectroscopic observa-
tions seem to favour the short period.

Flammarion thinks that "nothing certain can
be descried upon the surface of Venus, and that
whatever has hitherto been written regarding its
period of rotation must be considered null and
void"; and again he says, "Nothing can be
affirmed regarding the rotation of Venus, inas-
much as the absorption of its immense atmosphere
certainly prevents any detail on its surface from
being perceived." 1

The eminent Swedish physicist Arrhenius thinks,
however, that the dense atmosphere and clouds
1 Knowledge, November 1, 1897, pp. 200, 2G1.

VENUS 23

of Venus are in favour of a rapid rotation 011 its
axis.1 He thinks that the mean temperature of
Venus may " not differ much from the calculated
temperature 104° F." " Under these circumstances
the assumption would appear plausible that a
very considerable portion of the surface of Venus,
and particularly the districts about the poles,
would be favourable to organic life." 2

The " secondary light of Venus," or the visibility
of the dark side, seems to have been first mentioned
by Derham in his Astro Theology published in
1715. He speaks of the visibility of the dark
part of the planet's disc "by the aid of a light
of a somewhat dull and ruddy colour." The date
of Derham's observation is not given, but it seems
to have been previous to the year 1714. The
light seems to have been also seen by a friend
of Derham. We next find observations by
Christfried Kirch, assistant astronomer to the
Berlin Academy of Sciences, on June 7, 1721, and
March 8, 1726. These observations are found in
his original papers, and were printed in the
Astronomische Nachrichten, No. 1586. On the
first date the telescopic image of the planet
was "rather tremulous," but in 1726 he noticed
that the dark part of the circle seemed to belong
to a smaller circle than the illuminated portion
of the disc.3 The same effect was also noted by

1 Worlds in the Making, p. 61. 2 Ibid., p. 48.

3 Nature, June 1, 1876.

24 ASTRONOMICAL CURIOSITIES

Webb.1 A similar illusion is seen in the case of
the crescent moon, and this has given rise to the
saying, " the old moon in the new moon's arms."

We next come, in order of date, to an observa
tion made by Andreas Mayer, Professor of
Mathematics at Grief swald in Prussia. The
observation was made on October 20, 1759, and
the dark part of Venus was seen distinctly by
Mayer. As the planet's altitude at the time was
not more than 14° above the horizon, and its
apparent distance from the sun only 10°, the
phenomenon — as Professor Safarik has pointed
out — " must have had a most unusual intensity."

Sir William Herschel makes no mention of
having ever seen the " secondary light " of Venus,
although he noticed the extension of the horns
beyond a semicircle.

In the spring and summer of the year 1793,
Von Hahii of Remplin in Mecklenburg, using
excellent telescopes made by Dollond and
Herschel, saw the dark part of Venus on several
occasions, and describes the light as "grey
verging upon brown."

Schroter of Lilienthal — the famous observer
of the moon — saw the horns of the crescent of
Venus extended many degrees beyond the semi-
circle on several occasions in 1784 and 1795, and
the border of the dark part faintly lit up by a
dusky grey light. On February 14, 1806, at
1 Cel, Object*, vol. i. p. CC (5th Edition).

VENUS 25

7 P.M. he saw the whole of the dark part visible
with an ash-coloured light, and he was satisfied
that there was no illusion. On January 24 of
the same year, 1806, Harding at Gottingen, using
a reflector of 9 inches aperture and power 84,
saw the dark side of Venus " shining with a pale
ash-coloured light," and very visible against the
dark background of the sky. The appearance
was seen with various magnifying powers, and
he thought that there could be no illusion. In
fact the phenomenon was as evident as in the
case of the moon. Harding again saw it on
February 28 of the same year, the illumination
being of a reddish grey colour, " like that of the
moon in a total eclipse."

The " secondary light " was also seen by Pastorff
in 1822, and by Gruithuisen in 1825. Since 1824
observations of the " light" were made by Berry,
Browning, Guthrie, Langdon, Noble, Prince, Webb,
and others. Webb saw it with powers of 90 and
212 on a 9*38-inch mirror, and found it " equally
visible when the bright crescent was hidden by a
field bar." l

Captain Noble's observation was rather unique.
He found that the dark side was " always dis-
tinctly and positively darker than the background
upon which it is projected."

The "light" was also seen by Lymaii in
America in 1867, and by Safarik at Prague. In
1 Celestial Objects, vol. i. p. 63 (5th Edition).

26 ASTRONOMICAL CURIOSITIES

1871 the whole disc of Venus was seen by Pro-
fessor Winnecke.1 On the other hand, Winnecke
stated that he only saw it twice in 24 years ; and
the great observers Dawes and Madler never saw
it at all ! 2

Various attempts have been made to explain
the visibility— at times — of the " dark side " of
Venus. The following may be mentioned3: — (1)
Reflected earth-light, analogous to the dark side
of the crescent moon. This explanation was advo-
cated by Harding, Schroter, and others. But,
although the earth is undoubtedly a bright object
in the sky of Venus, the explanation is evidently
quite inadequate. (2) Phosphorescence of the
planet's atmosphere. This has been suggested
by some observers. (3) Visibility by contrast, a
theory advanced by the great French astronomer
Arago. (4) Illumination of the planet's surface
by an aurora borealis. This also seems rather
inadequate, but would account for the light being
sometimes visible and sometimes not. (5) Lumi-
nosity of the oceans — if there be any — on Venus.
But this also seems inadequate. (6) A planetary
surface glowing with intense heat. But this
seems improbable. (7) The Kunstliche Feuer
(artificial fire) of Gruithuisen, a very fanciful
theory. Flammarion thinks that the visibility of
the dark side may perhaps be explained by its

1 Ast. Nacli. No. 1863. 2 Nature, June 1, 1876.

3 Ibid., June 8, 1876.

VENUS 27

projection 011 a somewhat lighter background,
such as the zodiacal light, or an extended solar
envelope.1

It will be seen that none of these explanations
are entirely satisfactory, and the phenomenon, if
real, remains a sort of astronomical enigma. The
fact that the "light" is visible on some occasions
and not on others would render some of the
explanations improbable or even inadmissible.
But the condition of the earth's atmosphere at
times might account for its invisibility on many
occasions.

A curious suggestion was made by Zollner,
namely, that if the secondary light of Venus
could be observed with the spectroscope it would
show bright lines ! But such an observation
would be one of extreme difficulty.

M. Hansky finds that the visibility of the
"light" is greater during periods of maximum
solar activity — that is, at the maxima of sun spots.
This he explains by the theory of Arrhenius, in
which electrified " ions emitted by the sun cause
the phenomena of terrestrial magnetic storms
and auroras." " In the same way the dense
atmosphere of Venus is rendered more phos-
phorescent, and therefore more easily visible by
the increased solar activity." 2 This seems a very
plausible hypothesis.

On the whole the occasional illumination of the

1 Nature, October 17, 1895. > 11ml, July 27, 1905.

28 ASTRONOMICAL CURIOSITIES

night side of Venus by a very brilliant aurora
(explanation (4) above) seems to the present
writer to be the most probable explanation.
Gruithuisen's hypothesis (7) seems utterly im-
probable.

There is a curious apparent anomaly about
the motion of Venus in the sky. Although the
planet's period of revolution round the sun is
224'7 days, it remains on the same side of the sun,
as seen from the earth, for 290 days. The reason
of this is that the earth is going at the same time
round the sun in the same direction, though at a
slower pace ; and Venus must continue to appear
on the same side of the sun until the excess of her
daily motion above that of the earth amounts to
179°, and this at the daily rate of 37' will be about
290 days/

Several observations have been recorded of a
supposed satellite of Venus. But the existence
of such a body has never been verified. In the
year 1887, M. Stroobant investigated the various
accounts, and came to the conclusion that in
several at least of the recorded observations the
object seen was certainly a star. Thus, in the
observation made by Rcedickcer and Boserup on
August 4, 1761, a satellite and star are recorded
as having been seen near the planet. M.
Stroobant finds that the supposed " satellite "
was the star x* Orionis, and the " star " %. Orionis.
1 Cekstial Cycle, p. 107.

VENUS 29

A supposed observation of a satellite made by
Horrebow 011 January 3, 1768, was undoubtedly
0 Librae. M. Stroobant found that the supposed
motion of the " satellite " as seen by Horrebow is
accurately represented by the motion of Venus
itself during the time of observation. In most
of the other supposed observations of a satellite
a satisfactory identification has also been found.
M. Stroobant finds that with a telescope of
0 inches aperture, a star of the 8th or even the
9th magnitude can be well seen when close
to Venus.1

On the night of August 13, 1892, Professor
Barnard, while examining Venus with the great
36-inch telescope of the Lick Observatory, saw a
star of the 7th magnitude in the same field with
the planet. He carefully determined the exact
position of this star, and found that it is not
in Argelander's great catalogue, the Durch-
musterung. Prof. Barnard finds that owing to
elongation of Venus from the sun at the time of
observation the star could not possibly be an
intra-Mercurial planet (that is, a planet revolving
round the sun inside the orbit of Mercury) ; but
that possibly it might be a planet revolving
between the orbits of Venus and Mercury. As
the brightest of the minor planets — Ceres, Pallas,
Juno, and Vesta — were not at the time near the
position of the observed object, the observation
1 Nature, October 6, 1887.

30 ASTRONOMICAL CURIOSITIES

remains unexplained. It might possibly have
been a nova, or temporary star.1

Scheuten is said to have seen a supposed satellite
of Venus following the planet across the sun at
the end of the transit of June 6, 1761.2

Humboldt speaks of the supposed satellite of
Venus as among " the astronomical myths of an
uncritical age." 3

An occultation of Venus by the moon is
mentioned in the Chinese Annals as having
occurred on March 19, 361 A.D., and Tycho Bralie
observed another on May 23, 1587.*

A close conjunction of Venus and Reguhi3
(a Leonis) is recorded by the Arabian astronomer,
Ibii Yunis, as having occurred on September 9, 885
A.D. Calculations by Hind show that the planet
and star were within 2' of arc on that night, and
consequently would have appeared as a single
star to the naked eye. The telescope had not
then been invented.5

Seen from Venus, the maximum apparent dis-
tance between the earth and moon would vary
from about 5' to 31'.6

It is related by Arago that Buonaparte, when
going to the Luxembourg in Paris, where the

1 Ast. Nach., No. 4106.

2 Copernicus, vol. ii. p. 168.

3 Cosmos, vol. iv. p. 476, footnote.

4 Denning, Telescopic Worlifor Starlight Kveningg, p. 153.
* Ibid., p. 154.

6 Nature, July 13, 1876.

VENUS 31

Directory were giving a fete in his honour, was
very much surprised to find the crowd assembled
in the Rue de Touracour '* pay more attention to
a region of the heavens situated above the palace
than to his person or the brilliant staff that
accompanied him. He inquired the cause and
learned that these curious persons were observing
with astonishment, although it was noon, a star,
which they supposed to be that of the conqueror
of Italy — an allusion to which the illustrious
general did not seem indifferent, when he himself,
with his piercing eyes, remarked the radiant
body." The " star" in question was Venus.1

1 P. M. Ryves in Knowledge, June 1, 1897, p. 144.

CHAPTER IV

The Earth

THE earth being our place of abode is, of
course, to us the most important planet
in the solar system. It is a curious
paradox that the moon's surface (at least the
visible portion) is better known to us than the
surface of the earth. Every spot on the moon's
visible surface equal in size to say Liverpool or
Glasgow is well known to lunar observers,
whereas there are thousands of square miles on
the earth's surface — for example, near the poles
and in the centre of Australia — which are wholly
unknown to the earth's inhabitants ; and are
perhaps likely to remain so.

Many attempts have been made by "para-
doxers " to show that the earth is a flat plane and
not a sphere. But M. Ricco has found by actual
experiment that the reflected image of the
setting sun from a smooth sea is an elongated
ellipse. This proves mathematically beyond all
doubt that the surface of the sea is spherical ; for
the reflection from a plane surface would be

THE EARTH 33

necessarily circular. The theory of a " flat
earth" is therefore proved to be quite unten-
able, and all the arguments (?) of the "earth
flatteners" have now been — like the French
Revolution — " blown into space."

The pole of minimum temperature in the
northern hemisphere, or "the pole of cold," as
it has been termed, is supposed to lie near
Werchojansk in Siberia, where a temperature of
nearly — 70° has been observed.

From a series of observations made at Annapolis
(U.S.A.) on the gradual disappearance of the blue
of the sky after sunset, Dr. See finds that the
extreme height of the earth's atmosphere is about
130 miles. Prof. Newcomb finds that meteors first
appear at a mean height of about 74 miles.1

An aurora seen in Canada on July 15, 1893,
was observed from stations 110 miles apart, and
from these observations the aurora was found to
lie at a height of 166 miles above the earth's
surface. It was computed that if the auroral
"arch maintained an equal height above the
earth its ends were 1150 miles away, so that the
magnificent sight was presented of an auroral
belt in the sky with 2300 miles between its two
extremities." 2

" Luminous clouds " are bright clouds sometimes
seen at night near the end of June and beginning

1 Bulletin, Ast. Soc. de France, August, 1905.

2 Xature, April 5, 1894.

34* ASTRONOMICAL CURIOSITIES

of July. They appear above the northern horizon
over the sun's place about midnight, and evidently
lie at a great height above the earth's surface.
Observations made in Germany by Dr. Jesse, and
in England by Mr. Backhouse, in the years 1885-91,
show that the height of these clouds is nearly
constant at about 51 miles.1 The present writer
has seen these remarkable clouds on one or two
occasions in County Sligo, Ireland, during the
period above mentioned.

M. Montigny has shown that " the approach of
violent cyclones or other storms is heralded by an
increase of scintillation" (or twinkling of the
stars). The effect is also very evident when such
storms pass at a considerable distance. He has
also made some interesting observations (especi-
ally on the star Capella), which show that, not
only does scintillation increase in rainy weather,
but that "it is very evident, at such times, in
stars situated at an altitude at which on other
occasions it would not be perceptible at all ; thus
confirming the remark of Humboldt's with regard
to the advent of the wet season in tropical
countries." 2

In a paper on the subject of " Optical Illusions "
in Popular Astronomy, February, 1906, Mr.

1 Nature, May 14, 1896. Some have attributed these "luminous
clouds " to light reflected from the dust of the Krakatoa eruption
(1883).

- The Observatory, 1877, p, 90.

THE EARTH 35

Arthur K. Bartlett, of Batter Creek, Michigan
(U.S.A.), makes the following interesting re-
marks : —

" The lunar halo which by many persons is
regarded as a remarkable and unexplained
luminosity associated with the moon, is to
meteorological students neither a mysterious nor
an anomalous occurrence. It has been frequently
observed and for many years thoroughly under-
stood, and at the present time admits of an easy
scientific explanation. It is an atmospheric ex-
hibition due to the refraction and dispersion of
the moon's light through very minute ice crystals
floating at great elevations above the earth, and
it is explained by the science of meteorology, to
which it properly belongs ; for it is not of
cosmical origin, and in no way pertains to
astronomy, as most persons suppose, except as
it depends on the moon, whose light passing
through the atmosphere, produces the luminous
halo, which as will be seen, is simply an optical
illusion, originating, not in the vicinity of the
moon — two hundred and forty thousand miles
away — but just above the earth's surface, and
within the aqueous envelope that surrounds it 011
all sides. ... A halo may form round the sun as
well as the moon . . . but a halo is more fre-
quently noticed round the moon for the reason
that we are too much dazzled by the sun's light
to distinguish faint colours surrounding its disc,
and to see them it is necessary to look through
smoked glass, or view the sun by reflection from
the surface of still water, by which its brilliancy
is very mvich reduced." . . .

" A ' corona ' is an appearance of faintly coloured
ings often seen around the sun and moon when

36 ASTRONOMICAL CURIOSITIES

a light fleecy cloud passes over them, and should
not be mistaken for a halo, which is much larger
and more complicated in its structure. These
two phenomena are frequently confounded by
inexperienced observers." With these remarks
the present writer fully concurs.
Mr. Bartlett adds —

"As a halo is never seen except when the
sky is hazy, it indicates that moisture is ac-
cumulating in the atmosphere which will form
clouds, and usually result in a storm. But the
popular notion that the number of bright stars
visible within the circle indicates the number
of days before the storm will occur, is without
any foundation whatever, and the belief is almost
too absurd to be refuted. In whatever part of
the sky a lunar halo is seen, one or more bright
stars are always sure to be noticed inside the
luminous ring, and the number visible depends
entirely upon the position of the moon. More-
over, when the sky within the circle is examined
with even a small telescope, hundreds of stars are
visible where only one, or perhaps two or three,
are perceived with the naked eye."

It is possible to have five Sundays in February
(the year must of course be a " leap year "). This
occurred in the year 1880, Sunday falling on
February 1, 8, 15, 22, and 29. But this will not
happen again till the year 1920. No century year
(such as 1900, 2000, etc.) could possibly have five
Sundays in February, aud the Rev. Richard
Campbell, who investigated this matter, finds

THE EARTH 37

the following sequence of years in which five
Sundays occur in February: 1604, 1632, 1660,
1688, 1728, 1756, 1784, 1824, 1852, 1880, 1920, 1948,
1976.1

In an article on "The Last Day and Year of
the Century: Remarks on Time Reckoning," in
Nature, September 10, 1896, Mr. W. T. Lynn, the
eminent astronomer, says, " The late Astronomer
Royal, Sir George Airy, once received a letter
requesting him to settle a dispute which had
arisen in some local debating society, as to which
would be the first day of the next century. His
reply was, 'A very little consideration, will
suffice to show that the first day of the twentieth
century will be January 1, 1901.' Simple as the
matter seems, the fact that it is occasionally
brought into question shows that there is some
little difficulty connected with it. Probably,
however, this is in a great measure due to the
circumstance that the actual figures are changed
on January 1, 1900, the day preceding being
December 31, 1899. A century is a very definite
word for an interval respecting which there is no
possible room for mistake or difference of opinion.
But the date of its ending depends upon that of
its beginning. Our double system of backward
and forward reckoning leads to a good deal of
inconvenience. Our reckoning supposes (what we
know was not the case, but as an era the date
1 Popular Astronomy, vol. 11 (1903), p. 293.

38 ASTRONOMICAL CURIOSITIES

does equally well) that Christ was born at the end
of B.C. 1. At the end of A.D. 1, therefore, one year
had elapsed from the event, at the end of A.D.
100, one century, and at the end of 1900, nineteen
centuries. ... It is clear, then, that the year, as
we call it, is an ordinal number, and that 1900
years from the birth of Christ (reckoning as we do
from B.C. 1) will not be completed until the end of
December 31 in that year, the twentieth century
beginning with January 1, 1901, that is (to be
exact) at the previous midnight, when the day
commences by civil reckoning." With these re-
marks of Mr. Lynn I fully concur, and, so far as I
know, all astronomers agree with him. As the
discussion will probably again arise at the end of
the twentieth century, I would like to put on
record here what the scientific opinion was at the
close of the nineteenth century.

Prof. E. Rutherford, the well-known authority
on radium, suggests that possibly radium is
a source of heat from within the earth. Traces
of radium have been detected in many rocks
and soils, and even in sea water. Calcula-
tion shows that the total amount distributed
through the earth's crust is enormously large,
although relatively small " compared with the
annual output of coal for the world." The
amount of radium necessary to compensate for
the present loss of heat from the earth "corre-
sponds to only five parts in one hundred million

THE EARTH 39

millions per unit mass," and the " observations of
Elster and Gertel show that the radio-activity
observed in soils corresponds to the presence of
about this proportion of radium." 1

The earth has 12 different motions. These are
as follows : —

1. Rotation 011 its axis, having a period of 24
hours.

2. Revolution round the sun ; period 365J days.

3. Precession ; period of about 25,765 years.

4. Semi-lunar gravitation ; period 28 days.

5. Nutation ; period 18 J years.

6. Variation in obliquity of the ecliptic ; about
47" in 100 years.

7. Variation of eccentricity of orbit.

8. Change of line of apsides ; period about 21,000
years.

9. Planetary perturbations.

10. Change of centre of gravity of whole solar
system.

11. General motion of solar system in space.

12. Variation of latitude with several degrees
of periodicity.2

"An amusing story has been told which
affords a good illustration of the ignorance and
popular notions regarding the tides prevailing
even among persons of average intelligence.
1 Tell me,' said a man to an eminent living English

1 Popular Astronomy, vol. 13 (1905), p. 226.

2 Nature, July 25, 1901 (from Flammftrion). -

40 ASTRONOMICAL CURIOSITIES

astronomer not long ago, * is it still considered
probable that the tides are caused by the moon ? '
The man of science replied that to the best of
his belief it was, and then asked in turn whether
the inquirer had any serious reason for question-
ing the relationship. 'Well, I don't know,' was
the answer ; * sometimes when there is no moon
there seems to be a tide all the same.' " ! 1

With reference to the force of gravitation, on
the earth and other bodies in the universe, Mr.
William B. Taylor has well said, "With each
revolving year new demonstrations of its abso-
lute precision and of its universal domination
serves only to fill the mind with added wonder
and with added confidence in the stability and the
supremacy of the power in which has been found
no variableness neither shadow of turning, but
which— the same yesterday, to-day and for ever —

" Lives through all life, extends through all extent,
Spreads undivided, operates unspent." 2

With reference to the habitability of other
planets, Tennyson has beautifully said —

'* Venus near her ! smiling downwards at this earthlier earth of

ours,

Closer on the sun, perhaps a world of never fading flowers.
Hesper, whom the poets call'd the Bringer home of all good

things ;
All good things may move in Hesper ; perfect people, perfect

kings.

1 Popular Astronomy, Vol. 11 (1903), p. 496.

2 Kinetic Theories of Gravitation, Washington, 1877.

THE EARTH 41

Hesper — Venus—were we native to that splendour, or in Mars,
We should see the globe we groan in fairest of their evening

stars.
Could we dream of war and carnage, craft and madness, lust

and spite,

Roaring London, raving Paris, in that spot of peaceful light ?
Might we not in glancing heavenward on a star so silver fair,
Yearn and clasp the hands, and murmur, * Would to God that

we were there ! ' "

The ancient Greek writer, Diogenes Laertius,
states that Anaximander (610-547 B.C.) believed
that the earth was a sphere. The Greek words
are : /UO-T/I/ re rrjv yrjv /ceicrtfat, Kevrpv rd&v €TT€\ovorav
ovarav or^aipoetS^.1

With reference to the Aurora Borealis, the
exact nature of which is not accurately known,
" a good story used to be told some years ago of a
candidate who, undergoing the torture of a vivd
voce examination, was unable to reply satis-
factorily to any of the questions asked. * Come,
sir,' said the examiner, with the air of a man
asking the simplest question, ' explain to me the
cause of the aurora borealis.' 'Sir,' said the
unhappy aspirant for t physical honours, * I could
have explained it perfectly yesterday, but ner-
vousness has, I think, made me lose my memory.'
' This is very unfortu/iate,' said the examiner ;
' you are the only man who could have explained
this mystery, and you have forgotten it," ' 2 This
was written in the year 1899, and probably the

1 The Observatory, June, 1894, p. 208.

2 Nature, June 8, 1899.

42 ASTRONOMICAL CURIOSITIES

phenomenon of the aurora remains nearly as
great a mystery to-day. In 1839, MM. Bravais
and Lottin made observations on the aurora in
Norway in about N. latitude 70°. Bravais found
the height to be between 62 and 93 miles above
the earth's surface.

The cause of the so-called Glacial Epoch in
the earth's history has been much discussed. The
Russian physicist, Rogovsky, has advanced the
following theory —

" If we suppose that the temperature of the
sun at the present time is still increasing, or at
least has been increasing until now, the glacial
epoch can be easily accounted for. Formerly
the earth had a high temperature of its own,
but received a lesser quantity of heat from
the sun than now ; on cooling gradually, the
earth's surface attained such a temperature as
caused a great part of the surface of the northern
and southern hemispheres to be covered with ice ;
but the sun's radiation increasing, the glaciers
melted, and the climatic conditions became as
they are now. In a word, the temperature of the
earth's surface is a function of two quantities:
one decreasing (the earth's own heat), and the
other increasing (the sun's radiation), and conse-
quently there may be a minimum, and this
minimum was the glacial epoch, which, as shown
by recent investigations, those of Luigi de Marchi
(Report of G. Schiaparelli, Meteor olog. Zeitschr.,
30, 130-136, 1895), are not local, but general for
the whole earth " fc (see also M. Neumahr,
Erdegeschicht).1

1 AstropliywalJournal, vol. 14 (1901), p. 238, footnote.

THE EARTH 43

Prof. Percival Lowell thinks that the life of
geological palaeozoic times was supported by the
earth's internal heat, which maintained the ocean
at a comparatively warm temperature.1

The following passage in the Book of the
Maccabees may possibly refer to an aurora —

" Now about this time Antiochus made his
second inroad into Egypt. And it so befell that
throughout all the city, for the space of almost
forty days, there appeared in the midst of the
sky horsemen in swift motion, wearing robes
inwrought with gold and carrying spears, equipped
in troops for battle ; and drawing of swords ; and
on the other side squadrons of horse in array ;
and encounters and pursuits of both armies ; and
shaking of shields, and multitudes of lances, and
casting of darts, and flashing of golden trappings,
and girding on of all sorts of armour. Wherefore
all men besought that the vision might have been
given for food." 2

According to Laplace "the decrease of the
mean heat of the earth during a period of 2000
years has not, taking the extremist limits,
diminished as much as ^th of a degree
Fahrenheit." 3

From his researches on the cause of the Preces-
sion of the Equinoxes, Laplace concluded that " the
motion of the earth's axis is the same as if the

1 Mars as the Abode of Life, p. 52.

2 Second Book of the Maccabees v. 1-4 (Revised Edition).
8 Humboldt's Cosmos, vol. i. p. 169 (Otte's translation).

44 ASTRONOMICAL CURIOSITIES

whole sea formed a solid mass adhering to its
surface." l

Laplace found that the major (or longer) axis
of the earth's orbit coincided with the line of
Equinoxes in the year 4107 B.C. The earth's
perigee then coincided with the autumnal equinox.
The epoch at which the major axis was perpen-
dicular to the line of equinoxes fell in the year
1250 A.D.2

Leverrier has found the minimum eccentricity
of the earth's orbit round the sun to be 0*0047 ; so
that the orbit will never become absolutely
circular, as some have imagined.

Laplace says —

"Astronomy considered in its entirety is the
finest monument of the human mind, the noblest
essay of its intelligence. Seduced by the illu-
sions of the senses and of self -pride, for a long
time man considered himself as the centre of
the movement of the stars ; his vain-glory has
been punished by the terrors which his own
ideas have inspired. At last the efforts of
several centuries brushed aside the veil which
concealed the system of the world. We discover
ourselves upon a planet, itself almost imperceptible
in the vast extent of the solar system, which in
its turn is only an insensible point in the immen-
sity of space. The sublime results to which this
discovery has led should suffice to console us for
our extreme littleness, and the rank which it
assigns to the earth. Let us treasure with

1 Quoted by Grant in History of Physical Astronomy, p. 71.

2 Ibid., pp. 100, 101.

THE EARTH 45

solicitude, let us add to as we may, this store
of higher knowledge, the most exquisite treasure
of thinking beings." l

With reference to probable future changes in
climate, the great physicist, Arrhenius, says —

" We often hear lamentation that the coal stored
up in the earth is wasted by the present genera-
tion without any thought of the future, and we
are terrified by the awful destruction of life and
property which has followed the volcanic erup-
tions of our days. We may find a kind of consola-
tion in the consideration that here, as in every
other case, there is good mixed with evil. By the
influence of the increasing percentage of carbonic
acid in the atmosphere, we may hope to enjoy
ages with more equable and better climates,
especially as regards the colder regions of the
earth, ages when the earth will bring forth much
more abundant crops than at present, for the
benefit of rapidly propagating mankind." 2

The night of July 1, 1908, was unusually bright.
This was noticed in various parts of England and
Ireland, and by the present writer in Dublin.
Humboldt states that " at the time of the new
moon at midnight in 1743, the phosphorescence
was so intense that objects could be distinctly
recognized at a distance of more than 600 feet." 3

An interesting proof of the earth's rotation on
its axis has recently been found.

1 Exposition du Systtme du Monde, quoted by Carl Snyder in
The World Machine, p. 226.

2 Worlds in the Malting, p. 63.
* Cosmos, vol. i. p. 131.

46 ASTRONOMICAL CURIOSITIES

" In a paper in the Proceedings of the Vienna
Academy (June, 1908) by Herr Tumlirz, it is shown
mathematically that if a liquid is flowing outwards
between two horizontal discs, the lines of flow will
be strictly straight only if the discs and vessel be
at rest, and will assume certain curves if that vessel
and the discs are in rotation, as, for example, due
to the earth's rotation. An experimental arrange-
ment was set up with all precautions, and the
stream lines were marked with coloured liquids
and photographed. These were in general accord
with the predictions of theory and the supposition
that the earth is rotating about an axis." l

In a book published in 1905 entitled The
Rational Almanac, by Moses B. Cotsworth, of
York, the author states that (p. 397), "The ex-
planation is apparent from the Great Pyramid's
Slope, which conclusively proves that when it was
built the latitude of that region was 7°'l more
than at present. Egyptian Memphis now near
Cairo was then in latitude 37°'l, where Asia
Minor now ranges, whilst Syria would then be
where the Caucasus regions now experience those
rigorous winters formerly experienced in Syria."
But the reality of this comparatively great change
of latitude in the position of the Great Pyramid
can be easily disproved. Pytheas of Marseilles —
who lived in the time of Alexander the Great,
about 330 B.C. — measured the latitude of Marseilles
by means of a gnomon, and found it to be about
42° 56'f. As the present latitude of Marseilles is

1 The Olsm-atory, June, 1009, p. 2G1.

THE EARTH 47

43° 17' 50", no great change in the latitude could
have taken place in over 2000 years.1 From this
we may conclude that the latitude of the Great
Pyramid has not changed by 7°'l since its con-
struction. There is, it is true, a slow diminution
going on in the obliquity of the ecliptic (or inclina-
tion of the earth's axis), but modern observations
show that this would not amount to as much as
one degree in 6000 years. Eudemus of Rhodes — a
disciple of Aristotle (who died in 322 B.C.) — found
the obliquity of the ecliptic to be 24°, which
differs but little from its present value, 23° 27'.
Al-Sufi in the tenth century measured the latitude
of Schiraz in Persia, and found it 29° 30'. Its
present latitude is 29° 36' SO",2 so that evidently
there has been no change in the latitude in 900
years.

1 Astronomical Essays, pp. 61, G2.

2 Encyclopxdia Brilannica (Schiraz).

CHAPTER V

The Moon

THE total area of the moon's surface is about
equal to that of North and South America.
The actual surface visible at any one time
is about equal to North America.

The famous lunar observer, Schroter, thought
that the moon had an atmosphere, but estimated
its height at only a little over a mile. Its density
he supposed to be less than that of the vacuum in
an air-pump. Recent investigations, however,
seem to show that owing to its small mass and
attractive force the moon could not retain an
atmosphere like that of the earth.

Prof. N. S. Shaler, of Harvard (U.S.A.), finds
from a study of the moon (from a geological point
of view) with the 15-inch refractor of the Harvard
Observatory, that our satellite has no atmosphere
nor any form of organic life, and he believes that
its surface " was brought to its present condition
before the earth had even a solid crust." l

There is a curious illusion with reference to the
1 Monthly Notices, B.A.S., February, 1905.

THE MOON 49

moon's apparent diameter referred to by Proctor.1
If, when the moon is absent in the winter months,
we ask a person whether the moon's diameter is
greater or less than the distance between the stars
8 and e, and e and £ Orionis, the three well-known
stars in the " belt of Orion," the answer will pro-
bably be that the moon's apparent diameter is about
equal to each of these distances. But in reality
the apparent distance between S and c Orionis (or
between c and £, which is about the same) is more
than double the moon's apparent diameter. This
seems at first sight a startling statement ; but its
truth is, of course, beyond all doubt and is not
open to argument. Proctor points out that if a
person estimates the moon as a foot in diameter,
as its apparent diameter is about half a degree,
this would imply that the observer estimates the
circumference of the star sphere as about 720 feet
(360° x 2), and hence the radius (or the moon's
distance from the earth) about 115 feet. But in
reality all such estimates have 110 scientific (that
is, accurate) meaning. Some of the ancients, such
as Aristotle, Cicero, and Heraclitus, seem to have
estimated the moon's apparent diameter at about
a foot.2 This shows that even great minds may
make serious mistakes.

It has been stated by some writer that the
moon as seen with the highest powers of the great

1 Nature, March 3, 1870.

2 Hid., March 31, 1870, p. 557.

50 ASTRONOMICAL CURIOSITIES

Yerkes telescope (40 inches aperture) appears
"just as it would be seen with the naked eye if it
were suspended 60 miles over our heads." But
this statement is quite erroneous. The moon as
seen with the naked eye or with a telescope shows
us nearly a whole hemisphere of its surface. But
if the eye were placed only 60 miles from the
moon's surface, we should see only a small portion
of its surface. In fact, it is a curious paradox that
the nearer the eye is to a sphere the less we see of
its surface! The truth of this will be evident
from the fact that on a level plain an eye placed
at a height, say 5 feet, sees a very small portion
indeed of the earth's surface, and the higher we
ascend the more of the surface we see. I find
that at a distance of 60 miles from the moon's
surface we should only see a small portion of its
visible hemisphere (about ^th). The lunar
features would also appear under a different
aspect. The view would be more of a landscape
than that seen in any telescope. This view of the
matter is not new. It has been previously pointed
out, especially by M. Flammarion and Mr. Whit-
mell, but its truth is not, I think, generally
recognized. Prof. Newcomb doubts whether with
any telescope the moon has ever been seen so well
as it would be if brought within 500 miles of the
earth.

A relief map of the moon 19 feet in diameter
was added, in 1898, to the Field Columbian

THE MOON 51

Museum (U.S.A.). It was prepared with great
care from the lunar charts of Beer and Madler,
and Dr. Schmidt of the Athens Observatory, and
it shows the lunar features very accurately. Its
construction took five years.

On a photograph of a part of the moon's sur-
face near the crater Eratosthenes, Prof. William
H. Pickering finds markings which very much
resemble the so-called "canals" of Mars. The
photograph was taken in Jamaica, and a copy of it
is given in Prof. Pickering's book on the Moon,
and in Popular Astronomy, February, 1904.

Experiments made in America by Messrs.
Stebbins and F. C. Brown, by means of selenium
cells, show that the light of the full moon is about
nine times that of the half moon ; * and that " the
moon is brighter between the first quarter and
full than in the corresponding phase after full
moon." They also find that the light of the full
moon is equal to "0*23 candle power,"1 that is,
according to the method of measurement used in
America, its light is equal to 0*23 of a standard
candle placed at a distance of one metre (39'37
inches) from the eye.2

Mr. H. H. Kimball finds that no less than 52 per
cent, of the observed changes in intensity of the
" earth-shine " visible on the moon when at 01
near the crescent phase is due to the eccentricity

1 Prof. W. H. Pickering found 12 timea (eee p. 1).
* Nature, January 30, 1908.

52 ASTRONOMICAL CURIOSITIES

of the lunar orbit, and " this is probably much
greater than could be expected from any increase
or diminution in the average cloudiness over the
hemisphere of the earth reflecting light to the
moon." l

v The "moon maiden" is a term applied to a
fancied resemblance of a portion of the Sinus
Iridum to a female head. It forms the " pro-
montory " known as Cape Heraclides, and may be
looked for when the moon's "age" is about 11
days. Mr. C. J. Caswell, who observed it on
September 29, 1895, describes it as resembling " a
beautiful silver statuette of a graceful female
figure with flowing hair."

M. Landerer finds that the angle of polariza-
tion of the moon's surface — about 33° — agrees well
with the polarizing angle for many specimens of
igneous rocks (30° 51' to 33° 46'). The polarizing
angle for ice is more than 37°, and this fact
is opposed to the theories of lunar glaciation
advanced by some observers.2

Kepler states in his Somnium that he saw the
moon in the crescent phase on the morning and
evening of the same day (that is, before and after
conjunction with the sun). Kepler could see 14
stars in the Pleiades with the naked eye, so his
eyesight must have been exceptionally keen.

Investigations on ancient eclipses of the moon
show that the eclipse mentioned by Josephus as

1 Nature, September 5, 1901. " Ibid., July 31, 1890.

THE MOON 53

having occurred before the death of Herod is
probably that which took place 011 September 15,
B.C. 5. This occurred about 9.45 p.m. ; and probably
about six months before the death of Herod
(St. Matthew ii. 15).

The total lunar eclipse which occurred 011
October 4, 1884, was remarkable for the almost
total disappearance of the moon during totality.
One observer says that " in the open air, if one had
not known exactly where to look for it, one might
have searched for some time without discovering
it. I speak of course of the naked eye appear-
ance." * On the other hand the same observer,
speaking of the total eclipse of the moon on
August 23, 1877, which was a bright one, says —

" The moon even in the middle of the total phase
was a conspicuous object in the sky, and the
ruddy colour was well marked. In the very
middle of the eclipse the degree of illumination
was as nearly as possible equal all round the edge
of the moon, the central parts being darker than
those near the edge."

In Roger de Hovedin's Chronicle (A.D. 756) an
account is given of the occultation of " a bright
star," by the moon during a total eclipse. This is
confirmed by Simeon of Durham, who also dates
the eclipse A.D. 756. This is, however, a mistake,
the eclipse having occurred on the evening of
November 23, A.D. 755. Calvisius supposed that
1 Nature^ October 16, 1884.

54. ASTRONOMICAL CURIOSITIES

the occulted " star " might have been Aldebaran.
Pingre, however, showed that this was impossible,
and Struyck, in 1740, showed that the planet
Jupiter was the " star " referred to by the early
observer. Further calculations by Hind (1885)
show conclusively that Struyck was quite correct,
and that the phenomenon described in the old
chronicles was the occultation of Jupiter by
a totally eclipsed moon — a rather unique phe-
nomenon.1

An occultation of Mars by the moon is recorded
by the Chinese, on February 14, B.C. 69, and one
of Venus, on March 30, A.D. 361. These have
also been verified by Hind, and his calculations
show the accuracy of these old Chinese records.

It has been suggested that the moon may
possibly have a satellite revolving round it, as
the moon itself revolves round the earth. This
would, of course, form an object of great interest.
During the total lunar eclipses of March 10 and
September 3, 1895, a careful photographic search
was made by Prof. Barnard for a possible lunar
satellite. The eclipse of March 10 was not very
suitable for the purpose owing to a hazy sky, but
that of September 3 was " entirely satisfactory,"
as the sky was very clear, and the duration of
totality was very long. On the latter occasion " six
splendid " photographs were obtained of the total
phase with a 6-inch Willard lens. The result
1 Nature, February 19, 1885.

THE MOON 55

was that none of these photographs " show any-
thing which might be taken for a lunar satellite,"
at least any satellite as bright as the 10th or
12th magnitude. It is, of course, just possible
that the supposed satellite might have been behind
the moon during the totality.

With reference to the attraction between the
earth and moon, Sir Oliver Lodge says —

" The force with which the moon is held in its
orbit would be great enough to tear asunder a steel
rod 400 miles thick, with a tenacity of 30 tons to
the square inch, so that if the moon and earth
were connected by steel instead of gravity, a
forest of pillars would be necessary to whirl the
system once a month round their common centre
of gravity. Such a force necessarily implies
enormous tensure or pressure in the medium.
Maxwell calculates that the gravitational stress
near the earth, which we must suppose to exist in
the invisible medium, is 3000 times greater than
what the strongest steel can stand, and near the
sun it should be 2500 times as great as that." x

With reference to the names given to " craters "
on the moon, Prof. W. H. Pickering says,2 " The
system of nomenclature is, I think, unfortunate.
The names of the chief craters are generally those
of men who have done little or nothing for
selenography, or even for astronomy, while the
men who should be really commemorated are

1 Nature, January 14, 1909, p. 323.

• Photographic Atlas of the Moon, Annah of Harvard Observatory
vol. li. pp. 14, 15.

56 ASTRONOMICAL CURIOSITIES

represented in general by small and unimportant
craters," and again —

"A serious objection to the whole system
of nomenclature lies in the fact that it has
apparently been used by some selenographers,
from the earliest times up to the present, as a
means of satisfying their spite against some of
their contemporaries. Under the guise of pretend-
ing to honour them by placing their names in
perpetuity upon the moon, they have used their
names merely to designate the smallest objects
that their telescopes were capable of showing.
An interesting illustration of this point is found
in the craters of Galileo and Riccioli, which lie
close together on the moon. It will be remembered
that Galileo was the discoverer of the craters on
the moon. Both names were given by Riccioli,
and the relative size and importance of the craters
[Riccioli large, and Galileo very small] probably
indicates to us the relative importance that he
assigned to the two men themselves. Other
examples might be quoted of craters named in
the same spirit after men still living. . . . With
the exception of Maedler, one might almost say,
the more prominent the selenographer the more
insignificant the crater."

The mathematical treatment of the lunar theory
is a problem of great difficulty. The famous
mathematician, Euler, described it as incredibile
studium atque indefessus labor.1

With reference to the "earth-shine" on the
moon when in the crescent phase, Humbolclt
says, " Lambert made the remarkable observation
1 Nature, January 18, 1906.

THE MOON 57

(14th of February, 1774) of a change of the ash-
coloured moonlight into an olive-green colour,
bordering upon yellow. The moon, which then
stood vertically over the Atlantic Ocean, received
upon its night side the green terrestrial light, which
is reflected towards her when the sky is clear by
the forest districts of South America." 1 Arago
said, "II n'est done pas impossible, malgre tout
ce qu'un pareil resultat exciterait de surprise au
premier coup d'ceil qu'un jour les meteorologistes
aillent puiser dans 1' aspect de la Lune des notions
precieuses sur Vetat moyen de diaphanite de
1' atmosphere terrestre, dans les hemispheres qui
successivement concurrent a la production de la
lumiere cendree." 2

The " earth-shine " on the new moon was success-
fully photographed in February, 1895, by Prof.
Barnard at the Lick Observatory, with a 6-iiich
Willard portrait lens. He says —

"The earth-lit globe stands out beautifully
round, encircled by the slender crescent. All
the ' seas ' are conspicuously visible, as are also
the other prominent features, especially the region
about Tycho. Aristarchus and Copernicus appear
as bright specks, and the light streams from
Tycho are very distinct." 3

Kepler found that the moon completely dis-
appeared during the total eclipse of December 9,

1 Humboldt's Cosmos, vol. iv. p. 481. 2 Ibid,, p. 482.

3 Monthly Notices, B.A.S., June, 1895.

58 ASTRONOMICAL CURIOSITIES

1601, and Hevelius observed the same phenomenon
during the eclipse of April 25, 1642, when " not a
vestige of the moon could be seen." l In the total
lunar eclipse of June 10, 1816, the moon during
totality -was not visible in London, even with a
telescope ! l

The lunar mountains are relatively much higher
than those on the earth. Beer and Madler found
the following heights : Dorfel, 23,174 feet ; Newton,
22,141 ; Casatus, 21,102 ; Curtius, 20,632 ; Callippus,
18,946 ; and Tycho, 18,748 feet.2

Taking the earth's diameter at 7912 miles, the
moon's diameter, 2163 miles, and the height of
Mount Everest as 29,000 feet, I find that

Everest 1 Dorfel 1

:,and

Earth's diameter 1440* moon's diameter 492

From which it follows that the lunar mountains
are proportionately about three times higher than
those on the earth.

According to an hypothesis recently advanced
by Dr. See, all the satellites of the solar system,
including our moon, were " captured " by their
primaries. He thinks, therefore, that the " moon
came to earth from heavenly space." 3

1 Humboklt's Cosmo*, vol. iv. p. 483 (Otte's translation).

- Grant, History of Physical Astronomy, p. 229.

3 Popular Astronomy, vol. xvii. No. 6, p. 387 (June- July, 1909).

CHAPTER VI

Mars

MARS was called by the ancients " the
vanishing star," owing to the long
periods during which it is practically
invisible from the earth.1 It was also called
Trupo'ei? and Hercules.

I have seen it stated in a book on the " Solar
System" by a well-known astronomer that the
axis of Mars " is inclined to the plane of the orbit "
at an angle of 24° 50' ! But this is quite erroneous.
The angle given is the angle between the plane of
the planet's equator and the plane of its orbit,
which is quite a different thing. This angle,
which may be called the obliquity of Mars'
ecliptic, does not differ much from that of the
earth. Lowell finds it 23° 13' from observations
in 1907.2

The late Mr. Proctor thought that Mars is " far
the reddest star in the heavens ; Aldebaran and
Antares are pale beside him." 3 But this does not

1 Nature, October 7, 1875.

2 Mars as an Abode of Life (1908), p. 281.

3 Knoioledge, May 2, 188G.

60 ASTRONOMICAL CURIOSITIES

agree with my experience. Antares is to my eye
quite as red as Mars. Its name is derived from
two Greek words implying " redder than Mars."
The colour of Aldebaran is, I think, quite com-
parable with that of the " ruddy planet." In the
telescope the colour of Mars is, I believe, more
yellow than red, but I have not seen the planet
very often in a telescope. Sir John Herschel
suggested that the reddish colour of Mars may
possibly be due to red rocks, like those of the Old
Red Sandstone, and the red soil often associated
with such rocks, as I have myself noticed near
Torquay and other places in Devonshire.

The ruddy colour of Mars was formerly thought
to be due to the great density of its atmosphere.
But modern observations seem to show that the
planet's atmosphere is, on the contrary, much
rarer than that of the earth. The persistent
visibility of the markings on its surface shows
that its atmosphere cannot be cloud-laden like
ours ; and the spectroscope shows that the water
vapour present is — although perceptible — less
than that of our terrestrial envelope.

The existence of water vapour is clearly shown
by photographs of the planet's spectrum taken by
Mr. Slipher at the Lowell Observatory in 1908.
These show that the water vapour bands a and
near D are stronger in the spectrum of Mars than
in that of the moon at the same altitude.1
1 Nature, March 12, 1908.

MARS 61

The dark markings on Mars were formerly
supposed to represent water and the light parts
land. But this idea has now been abandoned.
Light reflected from a water surface is polarized
at certain angles. Prof. W. H. Pickering, in his
observations on Mars, finds no trace of polariza-
tion in the light reflected from the dark parts of
the planet. But under the same conditions he
finds that the bluish -black ring surrounding the
white polar cap shows a well-marked polarization
of light, thus indicating that this dark ring is
probably water.1

Projections on the limb of the planet have
frequently been observed in America. These are
known not to be mountains, as they do not re-
appear under similar conditions. They are sup-
posed to be clouds, and one seen in December,
1900, has been ^explained as a cloud lying at a
height of some 13 miles above the planet's surface
and drifting at the rate of about 27 miles an
hour. If there are any mountains on Mars they
have not yet been discovered.

The existence of the so-called " canals " of Mars is
supposed to be confirmed by Lowell's photographs
of the planet. But what these "canals" really
represent, that is the question. They have
certainly an artificial look about them, and they
form one of the most curious and interesting
problems in the heavens. Prof. Lowell says —
1 Bulletin, Ast. Soc. de France, April, 1899.

62 ASTRONOMICAL CURIOSITIES

" Most suggestive of all Martian phenomena are
the canals. Were they more generally observ-
able the world would have been spared much
scepticism and more theory. They may of course
not be artificial, but observations here [Flag-
staff] indicate that they are ; as will, I think,
appear from the drawings. For it is one thing to
see two or three canals and quite another to have
the planet's disc mapped with them on a most
elaborate system of triangulation. In the first
place they are this season (August, 1894) bluish-
green, of the same colour as the seas into which
the longer ones all eventually debouch. In the
next place they are almost without exception
geodetically straight, supernaturally so, and this
in spite of their leading in every possible direc-
tion. Then they are of apparently nearly
uniform width throughout their length. What
they are is another matter. Their mere aspect,
however, is enough to cause all theories about
glaciatioii fissures or surface cracks to die an
instant and natural death." l

Some of the observed colour-changes on Mars
are very curious. In April, 1905, Mr. Lowell
observed that the marking known as Mare
Erythrseurn, just above Syrtis, had "changed
from a blue-green to a chocolate-brown colour."
The season on Mars corresponded with our
February.

Signor V. ' Cerulli says that, having observed
Mars regularly for ten years, he has come to
the conclusion that the actual existence of the
" canals " is as much a subject for physiological

1 Astronomy and Astrophysics (1894), p. C49.

MARS 63

as for astronomical investigation. He states that
" the phenomena observed are so near the limit of
the range of the human eye that in observing
them one really experiences an effect accompany-
ing * the birth of vision.' That is to say, the eye
sees more and more as it becomes accustomed, or
strained, to the delicate markings, and thus the
joining up of spots to form * canals ' and the
gemination of the latter follow as a physiological
effect, and need not necessarily be subjective
phenomena seen by the unaccustomed eye." l

The possibility of life on Mars has been recently
much discussed ; some denying, others asserting.
M. E. Rogovsky says —

" As free oxygen and carbonic dioxide may
exist in the atmosphere of Mars, vegetable and
animal life is quite possible. If the temperature
which prevails upon Mars is nearer to —36° C.
than to —73° C., the existence of living beings
like ourselves is possible. In fact, the ice of
some Greenland and Alpine glaciers is covered
by red algse (Sphcerella nivalis) ; we find there
also different species of rotaloria, variegated
spiders, and other animals on the snow fields
illuminated by the sun; at the edges of glacier
snows in the Tyrol we see violet bells of
Soldanella pusilla, the stalks of which make
their way through the snow by producing heat
which melts it round about them. Finally the
Siberian town Verkhociansk, near Yakutsk, exists,
though the temperature there falls to — 69°*8 C.
and the mean temperature of January to — 51°'2,
and the mean pressure of the vapour of water is

1 Nature, April 20, 1905.

64 ASTRONOMICAL CURIOSITIES

less than 0*05mm. It is possible, therefore, that
living beings have become adapted to the con-
ditions now prevailing upon Mars after the lapse
of many ages, and live at an even lower tem-
perature than upon the earth, developing the
necessary heat themselves."

M. Rogovsky adds, " Water in organisms is
mainly a liquid or solvent, and many other
liquids may be the same. We have no reason
to believe that life is possible only under the
same conditions and with the same chemical
composition of organisms as upon the earth,
although indeed we cannot affirm that they
actually exist on Mars." l With the above views
the present writer fully concurs.

Prof. Lowell thinks that the polar regions of
Mars, both north and south, are actually warmer
than the corresponding regions of the earth,
although the mean temperature of the planet is
probably twelve degrees lower than the earth's
mean temperature.2

A writer in Astronomy and Astrophysics (1892,
p. 748) says —

" Whether the planet Mars is inhabited or not
seems to be the all-absorbing question with the
ordinary reader. With the astronomer this
query is almost the last thing about the planet
that he would think of when he has an oppor-
tunity to study its surface markings ... no

1 Astrophysical Journal, vol. 14 (1901), p. 258.

2 Nature, August 22, 1907.

MARS 65

astronomer claims to know whether the planet
is inhabited or not."

Several suggestions have been made with
reference to the possibility of signalling to Mars.
But, as Mr. Larkin of Mount Lowe (U.S.A.) points
out, all writers on this subject seem to forget the
fact that the night side of two planets are never
turned towards each other. " When the sun is
between them it is day on the side of Mars which
is towards us, and also day on the side of the earth
Avhich is towards Mars. When they are on the
same side of the sun, it is day on Mars when
night on the earth, and for this reason they could
never see our signals. This should make it ap-
parent that the task of signalling to Mars is a
more difficult one than the most hopeful theorist
has probably considered. All this is under the
supposition that the Martians (if there are such)
are beings like ourselves. If they are not like us,
we cannot guess what they are like." l These
views seem to me to be undoubtedly correct, and
show the futility of visual signals. Electricity
might, however, be conceivably used for the
purpose ; but even this seems highly improbable.

Prof. Newcomb, in his work Astronomy for
Everybody, says with reference to this question,
" The reader will excuse me from saying nothing
in this chapter about the possible inhabitants of

1 Popular Astronomy, vol. 12 (1904), p. 679.

66 ASTRONOMICAL CURIOSITIES

Mars. He knows just as much about the subject
as I do, and that is nothing at all."

It is, however, quite possible that life in some
form may exist on Mars. As Lowell well says,
" Life but waits in the wings of existence for its
cue to enter the scene the moment the stage is
set." x With reference to the " canals " he says —

" It is certainly no exaggeration to say that they
are the most astonishing objects to be viewed
in the heavens. There are celestial sights more
dazzling, spectacles that inspire more awe, but
to the thoughtful observer who is privileged to
see them well, there is nothing in the sky so
profoundly impressive as these canals of Mars." 2

The eminent Swedish physicist Arrhenius thinks
that the mean annual temperature on Mars may
possibly be as high as 50° F. He says, " Some-
times the snow-caps on the poles of Mars dis-
appear entirely during the Mars summer ; this
never happens on our terrestrial poles. The mean
temperature of Mars must therefore be above zero,
probably about + 10° [Centigrade = 50° Fahren-
heit]. Organic life may very probably thrive,
therefore, on Mars." 3 He thinks that this excess
of mean temperature above the calculated tem-
perature may be due to an increased amount of
carbonic acid in the planet's atmosphere, and
says "any doubling of the percentage of carbon

1 Mars as an Abode of Life, p. 69. 2 Ibid., p. 146.

3 Worlds in the Making, p. 49.

MARS 67

dioxide in the air would raise the temperature
of the earth's surface by 4° ; and if the carbon
dioxide were increased fourfold, the temperature
would rise by 8°." l
Denning says, — 2

" A few years ago, when christening celestial
formations was more in fashion than it is now,
a man simply had to use a telescope for an
evening or two on Mars or the moon, and spice
the relation of his seeings with something in the
way of novelty, when his name would be pretty
certainly attached to an object and hung in the
heavens for all time! A writer in the Astro-
nomical Register for January, 1879, humorously
suggested that 'the matter should be put into
the hands of an advertising agent,' and 'made
the means of raising a revenue for astronomical
purposes.' Some men would not object to pay
handsomely for the distinction of having their
names applied to the seas and continents of Mars
or the craters of the moon."

An occultation of Mars by the moon is recorded
by Aristotle as having occurred on April 4,
357 B.C.3

Seen from Mars the maximum apparent distance
between the earth and moon would vary from 3^'
to nearly 17'.4

1 Worlds in the Making, p. 53.

2 Denning, Telescopic Work for Starlight Evenings, p. 158.

3 Ibid., p. 166.

4 Nature, July 13, 1876.

CHAPTER VII

The Minor Planets

UP to 1908 the number of minor planets (or
asteroids) certainly known amounted to
over 650.

From an examination of the distribution of the
first 512 of these small bodies, Dr. P. Stroobant
finds that a decided maximum in number occurs
between the limits of distance of 2'55 and 2*85
(earth's mean distance from sun = 1), " 199 of the
asteroids considered revolving in this annulus."
He finds that nearly all the asteroidal matter is
concentrated near to the middle of the ring in the
neighbourhood of the mean distance of 2*7, and
the smallest asteroids are relatively less numerous
in the richest zones.1

There are some " striking similarities " in the
orbits of some of the asteroids. Thus, in the
small planets Sophia (No. 251 in order of dis-
covery) and Magdalena (No. 318) we have the
mean distance of Sophia 3*10, and that of
Magdalena 3*19 (earth's mean distance = 1).
1 Nature, May 2, 1907.

THE MINOR PLANETS 69

The eccentricities of the orbits are 0'09 and 0'07 ;
and the inclinations of the orbits to the plane of
the ecliptic 10° 29' and 10° 33' respectively.1 This
similarity may be — and probably is — merely
accidental, but it is none the less curious and
interesting.

Some very interesting discoveries have recently
been made among the minor planets. The orbit
of Eros intersects the orbit of Mars ; and the
following have nearly the same mean distance
from the sun as Jupiter : —

Achilles (1906 TG), No. 588,
Patrocles (1906 XY), No. 617,
Hector (1907 XM), No. 624,

and another (No. 659) has been recently found.
Each of these small planets " moves approximately
in a vertex of an equilateral triangle that it forms
with Jupiter and the sun." 2 The minor planet
known provisionally as HN is remarkable for the
large eccentricity of its orbit (0*38), and its small
perihelion distance (1'6). When discovered it had
a very high South Declination (61J°), showing
that the inclination of the plane of its orbit to
the plane of the ecliptic is considerable.3

Dr. Bauschinger has made a study of the
minor planets discovered up to the end of 1900.

1 Nature, May 30, 1907.

2 Publications of the Astronomical Society of the Pacific,
August, 1908.

3 Monthly Notices, R.A.S., 1902, p. 291.

TO ASTRONOMICAL CURIOSITIES

He finds that the ascending nodes of the orbits
show a marked tendency to cluster near the
ascending node of Jupiter's orbit, a fact which
agrees well with Prof. Newcomb's theoretical
results. There seems to be a slight tendency for
large inclinations and great eccentricities to go
together ; but there appears to be no connection
between the eccentricity and the mean distance
from the sun. The longitudes of the perihelia
of these small planets "show a well-marked
maximum near the longitude of Jupiter's peri-
helion, and equally well-marked minimum near
the longitude of his aphelion," which is again in
good agreement with Newcomb's calculations.1
Dr. Bauschinger's diameter for Eros is 20 miles.
He finds that the whole group, including those
remaining to be discovered, would probably form
a sphere of about 830 miles in diameter.

The total mass of the minor planets has been
frequently estimated, but generally much too
high. Mr. B. M. Roszel of the John Hopkins
University (U.S.A.) has made a calculation of
the probable mass from the known diameter of
Vesta (319 miles, Pickering), and finds the volume
of the first 216 asteroids discovered. From this
calculation it appears that it would take 310
asteroids of the 6th magnitude, or 1200 of the
7th to equal the moon in volume. Mr. Rosxel
concludes that the probable mass of the whole
1 Monthly Notices, K.A.S., February, 1902, p. 291.

THE MINOR PLANETS 71

asteroidal belt is between ^th and r ^th of that
of the moon.1 Subsequently Mr. Roszel extended
his study to the mass of 311 asteroids,2 and found
a combined mass of about ^th of the moon's
mass.

Dr. Palisa finds that the recently discovered
minor planet (1905 QY) varies in light to a
considerable extent.3 This planet was discovered
by Dr. Max Wolf on August 23, 1905 ; but it
was subsequently found that it is identical with
one previously known, (167) Urda.4 The light
variation is said to be from the llth to the 13th
magnitude.5 Variation in some of the other
minor planets has also been suspected. Prof.
Wendell found a variation of about half a magni-
tude in the planet Eunomia (No. 15). He also
found that Iris (No. 7) varies about a quarter of a
magnitude in a period of about 6h 12m.6 But
these variations are small, and perhaps doubtful.
The variability of Eros is well known.

The planet Eros is a very interesting one. The
perihelion portion of its orbit lies between the
orbits of Mars and the earth, and the aphelion
part is outside the orbit of Mars. Owing to the
great variation in its distance from the earth the
brightness of Eros varies from the 6th to the 12th
magnitude. That is, when brightest, it is 250

1 Nature, May 24, 1894. " Ibid., February 14, 1895.

3 Ibid., September 14, 1905. 4 Ibid., September 21, 1905.
5 Ibid., September 28, 1905. 6 Ibid., July 13, 1905.

72 ASTRONOMICAL CURIOSITIES

times brighter than when it is faintest.1 This
variation of light, is of course, merely due to the
variation of distance ; but some actual variation in
the brightness of the planet has been observed.

It has been shown by Oeltzen and Valz that
Cacciatore's supposed distant comet, mentioned
by Admiral Smyth in his Bedford Catalogue,
must have been a minor planet.2

Dr. Max Wolf discovered 36 new minor planets
by photography in the years 1892-95. Up to
the latter year he had never seen one of these
through a telescope ! His words are, " Ich selsbt
habe noch nie einen meinen kleinen Planeten
am Himmel geseheii." 3

These small bodies have now become so
numerous that it is a matter of much difficulty
to follow them. At the meeting of the Royal
Astronomical Society on January 8, 1909, Mr.
G. F. Chambers made the following facetious
remarks —

" I would like to make a suggestion that has
been in my mind for several years past — that
it should be made an offence punishable by fine
or imprisonment to discover any more minor
planets. They seem to be an intolerable nuisance,
and are a great burden upon the literary gentle-
men who have to keep pace with them and record
them. I have never seen, during the last few

1 Nature, November 3, 1898.
- Ibid., July 14, 1881, p. 235.

3 Quoted in The Observatory, February, 1896, p. 104, from Ast.
Nach., No, 3319.

THE MINOR PLANETS 73

years at any rate, any good come from them,
or likely to come, and I should like to see the
supply stopped, and the energies of the German
gentlemen who find so many turned into more
promising channels."

Among the minor planets numbered 1 to 500,
about 40 " have not been seen since the year of
their discovery, and must be regarded as lost." ]

1 Monthly Notices, R.A.S., February, 1909.

CHAPTER VIII

Jupiter

THIS brilliant planet— only inferior to Venus
in brightness — was often seen by Bond
(Jun.) with the naked eye in "high and
clear sunshine " ; also by Denning, who has very
keen eyesight. Its brightness on such occasions
is so great, that — like Venus — it casts a distinct
shadow in a dark room.1

The great " red spot " 011 Jupiter seems to have
been originally discovered by Robert Hooke
on May 9, 1664, with a telescope of 2 inches
aperture and 12 feet focus. It seems to have
existed ever since ; at least the evidence is, accord-
ing to Denning, in favour of the identity of
Hooke's spot with the red spot visible in recent
years. The spot was also observed by Cassini
in the years 1665-72, and is sometimes called
'* Cassini's spot." But the real discoverer was
Hooke.2

The Orbit of Jupiter is so far outside the earth's

1 Celestial Objects, vol. i. p. 163.
- Nature, December 29, 1898.

JUPITER 75

orbit tliat there can be little visible in the way
of "phase" — as in the case of Mars, where the
" gibbous " phase is sometimes very perceptible.
Some books on astronomy state that Jupiter
shows no phase. But this is incorrect. A dis-
tinct, although very slight, gibbous appearance
is visible when the planet is near quadrature.
Webb thought it more conspicuous in twilight
than in a dark sky. With large telescopes,
Jupiter's satellites II. and III. have been seen —
in consequence of Jupiter's phase— to emerge
from occultation "at a sensible distance from
the limb." l

According to M. E. Rogovsky, the high " albedo
of Jupiter, the appearance of the clear (red) and
dark spots on its surface and their continual
variation, the different velocity of rotation of the
equatorial and other zones of its surface, and
particularly its small density (1*33, water as unity),
all these facts afford irrefragable proofs of the high
temperature of this planet. The dense and opaque
atmosphere hides its glowing surface from our
view, and we see therefore only the external
surface of its clouds. The objective existence of
this atmosphere is proved by the bands and lines
of absorption in its spectrum. The interesting
photograph obtained by Draper, September 27,
1879, in which the blue and green parts are more
brilliant for the equatorial zone than for the
1 Celestial Objects, vol. i. p. 166.

76 ASTRONOMICAL CURIOSITIES

adjacent parts of the surface, appears to show that
Jupiter emits its proper light. It is possible that
the constant red spot noticed on its surface by
several observers, as Gledhill, Lord Rosse, and
Copeland (1873), Russel and Bredikhm (1876), is
the summit of a high glowing mountain. G. W.
Hough considers Jupiter to be gaseous, and A.
Ritter inferred from his formulae that in this
case the temperature at the centre would be
600,000° C." l

The four brighter satellites of Jupiter are
usually known by numbers L, II., III., and IV. ; I.
being the nearest to the planet, and IV. the
farthest. III. is usually the brightest, and IV.
the faintest, but exceptions to this rule have been
noticed.

With reference to the recently discovered sixth
and seventh satellites of Jupiter, Prof. Perrine has
suggested that the large inclination of their orbits
to the plane of, the planet's equator seems to
indicate that neither of these bodies was originally
a member of Jupiter's family, but has been
" captured by the planet." This seems possible
as the orbits of some of the minor planets lie near
the orbit of Jupiter (see "Minor Planets"). A
similar suggestion has been made by Prof, del
Marmol.2

Many curious observations have been recorded

1 Aatrophysical Journal, vol. 14 (1901), pp. 248-9.
* Nature, August 27, 1908.

JUPITER 77

with reference to Jupiter's satellites ; some very
difficult of explanation. In 1711 Bianchini saw
satellite IV. so faint for more than an hour that
it was hardly visible ! A similar observation was
made by Lassell with a more powerful telescope
on June 13, 1849. Key, T. T. Smyth, and Denning
have also recorded unusual faintness.1 A very
remarkable phenomenon was seen by Admiral
Smyth, Maclear, and Pearson on June 26, 1828.
Satellite II., "having fairly entered on Jupiter,
was found 12 or 13 minutes afterwards outside the
limb, where it remained visible for at least 4
minutes, and then suddenly vanished." As Webb
says, " Explanation is here set at defiance ; demon-
strably neither in the atmosphere of the earth,
nor Jupiter, where and what could have been the
cause ? At present we can get no answer." 3
When Jupiter is in opposition to the sun — that is,
on the meridian at midnight — satellite I. has been
seen projected on its own shadow, the shadow
appearing as a dark ring round the satellite.

On January 28, 1848, at Cambridge (U.S.A.)
satellite III. was seen in transit lying between
the shadows of I. and II. and so black that it
could not be distinguished from the shadows,
" except by the place it occupied." This seems to
suggest inherent light in the planet's surface, as
the satellite was at the time illuminated by full

1 Webb's Celestial Objects, vol. i. p. 177.

2 Ibid., vol. i. p. 187.

78 ASTRONOMICAL CURIOSITIES

sunshine ; its apparent blackness being due to the
effect of contrast. Cassini on one occasion failed
to find the shadow of satellite I. when it should
have been on the planet's disc,1 an observation
which again points to the glowing light of Jupiter's
surface. Sadler and Trouvelot saw the shadow of
satellite I. double ! an observation difficult to
explain — but the same phenomenon was again
seen on the evening of September 19, 1891, by Mr.
H. S. Halbert of Detroit, Michigan (U.S.A.). He
says that the satellite "was in transit nearing
egress, and it appeared as a white disc against the
dark southern equatorial belt; following it was
the usual shadow, and at an equal distance from
this was a second shadow, smaller and not so dark
as the true one, and surrounded by a faint
penumbra."2

A dark transit of satellite III. was again
seen 011 the evening of December 19, 1891, by
two observers in America. One observer noted
that the satellite, when on the disc of the planet,
was intensely black. To the other observer
(Willis L. Barnes) it appeared as an ill-defined
dark image.3 A similar observation was made
on October 9 of the same year by Messrs. Gale
and Innes.4

1 Celestial Objects, vol. i. p. 186.

• Astronomy and Astrophysics, 1892, p. 87.

3 Ibid., 1892, pp. 94-5.

4 Observatory, December, 1891.

JUPITER 79

A " black transit " of satellite IV. was seen by
several observers in 1873, and by Prof. Barnard on
May 4, 1886. The same phenomenon was observed
011 October 30, 1903, in America, by Miss Anne S.
Young and Willis S. Barnes. Miss Young says —

" The ingress of the satellite took place at 8h 50|n
(E. standard time) when it became invisible upon
the background of the planet. An hour later it
was plainly visible as a dark round spot upon
the planet. It was decidedly darker than the
equatorial belt." x

The rather rare phenomenon of an occultation of
one of Jupiter's satellites by another was observed
by Mr. Apple, director of the Daniel Scholl
Observatory, Franklin and Marshall College,
Lancaster, Pa. (U.S.A.), on the evening of March
16, 1908. The satellites in question were I. and
II., and they were so close that they could not be
separated with the 11 '5-inch telescope of the
Observatory.2 One of the present writer's first
observations with a telescope is dated May 17,
1873, and is as follows : " Observed one of
Jupiter's satellites occulted (or very nearly so) by
another. Appeared as one with power 133 " (on
3-inch refractor in the Punjab). These satellites
were probably I. and II.

Jupiter has been seen on several occasions
apparently without his satellites; some being

1 Popular Astronomy, vol. 11 (1903), p. 574.

2 Ibid., October, 1908.

80 ASTRONOMICAL CURIOSITIES

behind the disc, some eclipsed in his shadow, and
some in transit across the disc. This phenomenon
was seen by Galileo, March 15, 1611 ; by Molyneux,
on November 12, 1681 ; by Sir William Herschel,
May 23, 1802; by Wallis, April 15, 1826; by
Greisbach, September 27, 1843 ; and by several
observers on four occasions in the years 1867-1895.1
The phenomenon again occurred on October 3,
1907, No. 1 being eclipsed and occulted, No. 2 in
transit, No. 3 eclipsed, and No. 4 occulted.2 It
was not, however, visible in Europe, but could
have been seen in Asia and Oceania.2 The
phenomenon will occur again on October 22,
1913.3

On the night of September 19, 1903, a star of
magnitude 6J was occulted by the disc of Jupiter.
This curious and rare phenomenon was photo-
graphed by M. Lucien Rudaux at the Observatory
of Donville, France.4 The star was Lalande
45698 (=BAC8129).5

Prof. Barnard, using telescopes with apertures
from 5 inches up to 36 inches (Lick), has failed to
see a satellite through the planet's limb (an
observation which has been claimed by other
astronomers). He says, "To my mind this has

1 Bulletin, Ast. Soc. de France, August, 1907.

2 Nature, August, 29 1907.

3 Ibid., March 7, 1907.

* Bulletin, Ast. Soc. de France, June, 1904.
5 The Observatory, October, 1903, p. 392.

JUPITER 81

been due to either poor seeing, a poor telescope,
or an excited observer." 1 He adds —

"I think it is high time that the astronomers
reject the idea that the satellites of Jupiter can be
seen through his limb at occultation. When the
seeing is bad there is a spurious limb to Jupiter
that well might give the appearance of trans-
parency at the occultation of a satellite. But
under first-class conditions the limb of Jupiter is
perfectly opaque. It is quibbling and begging the
question altogether to say the phenomenon of
transparency may be a rare one and so have
escaped my observations. Has any one said that
the moon was transparent when a star has been
seen projected on it when it ought to have been
behind it?"

Prof. Barnard and Mr. Douglass have seen
white polar caps 011 the third and fourth satellites
of Jupiter. The former says they are "exactly
like those on Mars." "Both caps of the fourth
satellite have been clearly distinguished, that at
the north being sometimes exceptionally large,
covering a surface equal to one-quarter or one-
third of the diameter of the satellite." 2 This was
confirmed on November 23, 1906, when Signor J.
Comas Sola observed a brilliant white spot sur-
rounded by a dark marking in the north polar
region of the third satellite. There were other
dark markings visible, and the satellite presented
the appearance of a miniature of Mars.8

1 Astronomy and Astrophysics, 1894, p. 277.

2 Nature, November 18, 1897.

3 Journal, B.A.A., January, 1907.

82 ASTRONOMICAL CURIOSITIES

An eighth satellite of Jupiter has recently
been discovered by Mr. Melotte at the Greenwich
Observatory by means of photography. It moves
in a retrograde direction round Jupiter in an
orbit inclined about 30° to that of the planet.
The period of revolution is about two years. The
orbit is very eccentric, the eccentricity being
about one-third, or greater than that of any
other satellite of the solar system. When
nearest to Jupiter it is about 9 millions of miles
from the planet, and when farthest about 20
millions.1 It has been suggested by Mr. George
Forbes that this satellite may possibly be identical
with the lost comet of Lexell which at its return
in the year 1779 became entangled in Jupiter's
system, and has not been seen since. If this be
the case, we should have the curious phenomenon
of a comet revolving round a planet !

According to Humboldt the four bright satellites
of Jupiter were seen almost simultaneously and
quite independently by Simon Marius at Ausbach
on December 29, 1609, and by Galileo at Padua on
January 7, 1610.2 The actual priority, there-
fore, seems to rest with Simon Marius, but the
publication of the discovery was first made by
Galileo in his Nuncius Siderius (1610).3 Grant,
however, in his History of Physical Astronomy,

1 Journal, B.A.A., February, 1909, p. 161.

2 Covmos, vol. ii. p. 703.

3 Ibid.

JUPITER 83

calls Simon Marius an " impudent pretender " !
(p. 79).

M. Dupret at Algiers saw Jupiter with the
naked eye on September 26, 1890, twenty minutes
before sunset.1

Humboldt states that he saw Jupiter with the
naked eye when the sun was from 18° to 20°
above the horizon.2 This was in the plains of
South America near the sea-level.

1 Denning, Telescopic Work for Starlight Evenings, p. 349.

2 Cosmos, vol. iii. p. 75.

CHAPTER IX

Saturn

TO show the advantages of large telescopes
over small ones, Mr. C. Roberts says
that "with the 25-inch refractor of the
Cambridge Observatory the view of the planet
Saturn is indescribably glorious ; everything I had
ever seen before was visible at a glance, and an
enormous amount of detail that I had never
even glimpsed before, after a few minutes'
observation." l

Chacornac found that the illumination of
Saturn's disc is the reverse of that of Jupiter,
the edges of Saturn being brighter than the
centre of the disc, while in the case of Jupiter —
as in that of the sun — the edges are fainter than
the centre.2 According to Mr. Denning, Saturn
bears satisfactorily "greater magnifying power
than either Mars or Jupiter." 3

At an occultation of Saturn by the moon,
which occurred on June 13, 1900, M. M. Honorat

1 Journal, B.A.A., June, 1896.

2 Celestial Objects, vol. i. p. 191.

3 Nature, May 30, 1901.

SATURN 85

noticed the great contrast between the slightly
yellowish colour of the moon and the greenish
tint of the planet.1

In the year 1892, when the rings of Saturn had
nearly disappeared, Prof. L. W. Underwood, of
the Underwood Observatory, Appleton, Wis-
consin (U.S.A.), saw one of Saturn's satellites
(Titan) apparently moving along the needlelike
appendage to the planet presented by the rings.
" The apparent diameter of the satellite so far
exceeded the apparent thickness of the ring
that it gave the appearance of a beautiful golden
bead moving very slowly along a fine golden
thread." 2

In 1907, when the rings of Saturn became
invisible in ordinary telescopes, Professor Camp-
bell, observing with the great Lick telescope,
noticed " prominent bright knots, visible . , .
in Saturn's rings. The knots were symmetrically
placed, two being to the east and two to the
west." This was confirmed by Mr. Lowell, who
says, " Condensations in Saturn's rings confirmed
here and measured repeatedly. Symmetric and
permanent." This phenomenon was previously
seen by Bond in the years 1847-56. Measures
of these light spots made by Prof. Barnard with
the 40 -inch Yerkes telescope show that the outer
one corresponded in position with the outer edge

1 Bulletin, Ast. Soc. de France, August, 1900.

2 Astronomy and Astrophysics, 1892.

86 ASTRONOMICAL CURIOSITIES

of the middle ring close to the Cassini division,
and the inner condensation, curious to say,
seemed to coincide in position with the "crape
ring." Prof. Barnard thinks that the thickness
of the rings "must be greatly under 100 miles,
and probably less than 50 miles," and he says —

"The important fact clearly brought out at
this apparition of Saturn is that the bright rings
are not opaque to the light of the sun — and this
is really what we should expect from the nature
of their constitution as shown by the theory of
Clerk Maxwell, and the spectroscopic results of
Keeler." 1

Under certain conditions it would be theo-
retically possible, according to Mr. Whitmell, to
see the globe of Saturn through the Cassini
division in the ring. But the observation would
be one of great difficulty and delicacy. The effect
would be that, of the arc of the division Avhich
crosses the planet's disc, "a small portion will
appear bright instead of dark, and may almost
disappear." 2

A remarkable white spot was seen on Saturn on
June 23, 1903, by Prof. Barnard, and afterwards
by Mr. Denning.3 Another white spot was seen
by Denning on July 9 of the same year.4 From
numerous observations of these spots, Denning
found a rotation period for the planet of about

1 Astrophysical Journal, January, 1908, p. 35.

- Nature, May 22, 1902. 3 Ibid., July 0, 1908.

4 Ibid., July 1C, 1903.

SATURN 87

10h 39 m 21s.1 From observations of the same spots
Signer Comas Sola found a period 10h 38m<4, a close
agreement with Denning's result. For Saturn's
equator, Prof. Hill found a rotation period of
10h 14m 23S>8, so that— as in the case of Jupiter —
the rotation is faster at the equator than in the
northern latitudes of the planet. A similar
phenomenon is observed in the sun. Mr. Denning's
results were fully confirmed by Herr Leo Brenner,
and other German astronomers.2

Photographs taken by Prof. V. M. Slipher in
America show that the spectrum of Saturn is
similar to that of Jupiter. None of the bands
observed in the planet's spectrum are visible in
the spectrum of the rings. This shows that if the
rings possess an atmosphere at all, it must be much
rarer than that surrounding the ball of the
planet. Prof. Slipher says that " none of the
absorption bands in the spectrum of Saturn can
be identified with those bands due to absorption
in the earth's atmosphere," and there is no trace
of aqueous vapour.3

In September, 1907, M. G. Fournier suspected
the existence of a " faint transparent and luminous
ring " outside the principal rings of Saturn. He
thinks that it may possibly be subject to periodical
fluctuations of brightness, sometimes being visible

1 Nature, September 24, 1903.

2 Ibid., October 8, 1903.

3 Astrophysical Journal, vol. 2G (1907), p. 60.

88 ASTRONOMICAL CURIOSITIES

and sometimes not.1 This dusky ring was again
suspected at the Geneva Observatory in October,
1908.2 M. Schaer found it a difficult object with a
16-inch Cassegraiii reflector. Prof. Stromgen at
Copenhagen, and Prof. Hartwig at Bamberg,
however, failed to see any trace of the supposed
ring.3 It was seen at Greenwich in October, 1908.

A "dark transit" of Saturn's satellite Titan
across the disc of the planet has been observed on
several occasions. It was seen by Mr. Isaac W.
Ward, of Belfast, on March 27, 1892, with a
4 '3-inch Wray refractor. The satellite appeared
smaller than its shadow. The phenomenon was
also seen on March 12 of the same year by the
Rev. A. Freeman, Mr. Mee, and M. F. Terby ; and
again on November 6, 1907, by Mr. Paul
Chauleur and Mr. A. B. Cobham.4

The recently discovered tenth satellite of Saturn,
Themis, was discovered by photography, and has
never been seen by the eye even with the largest
telescopes ! But its existence is beyond all doubt,
and its orbit round the planet has been calculated.

Prof. Hussey of the Lick Observatory finds that
Saturn's satellite Mimas is probably larger than
Hyperion. He also finds from careful measure-
ments that the diameter of Titan is certainly

1 Nature, January 30, 1908.

2 Ibid., October 15, 1908.

3 Ibid., October 29, 1908.

4 Journal, B.A.A., March, 1908, and June 22, 1908.

SATURN 89

overestimated, and that its probable diameter
is about 2500 miles.1

The French astronomer, M. Lucien Rudaux,
finds the following variation in the light of the
satellites of Saturn : —

Japetus from 9th magnitude to 12th
Ehea „ 9 „ 10-6

Dione „ 9'5 „ 10'5

Tethye „ 9'8 „ 10-5

Titan „ 8 „ 8'6

The variation of light is, he thinks, due to the
fact that the period of rotation of each satellite
is equal to that of their revolution round the
planet ; as in the case of our moon.2

The names of the satellites of Saturn are derived
from the ancient heathen mythology. They are
given in order of distance from the planet, the
nearest being Mimas and the farthest Themis.

1. Mimas was a Trojan born at the same time
as Paris.

2. Enceladus was son of Tartarus and Ge.

3. Tethys was wife of Oceanus, god of ocean
currents. She became mother of all the chief
rivers in the universe, as also the Oceanides or sea
nymphs.

4. Dione was one of the wives of Zeus.

5. Rhea was a daughter of Uranus. She
married Saturn, and became the mother of Vesta,
Ceres, Juno, and Pluto.

1 Nature, June 25, 1903.

2 Bulletin, Aft. Soc. de France, June, 1901.

90 ASTRONOMICAL CURIOSITIES

6. Titan was the eldest son of Uranus.

7. Hyperion was the god of day, and the father
of sun and moon.

8. Japetus was the fifth son of Uranus, and
father of Atlas and Prometheus.1

9. Phcebe was daughter of Uranus and Ge.

10. Themis was daughter of Uranus and Ge,
and, therefore, sister of Phoebe.

In a review of Prof. Comstock's Text Book of
Astronomy in The Observatory, November, 1901,
the remark occurs, " We are astonished to see
that Mr. Comstock alludes with apparent serious-
ness to the nine satellites of Saturn. As regards
the ninth satellite, we thought that all astronomers
held with Mrs. Betsy Prig on the subject of this
astronomical Mrs. Harris." This reads curiously
now (1909) when the existence of the ninth
satellite (Phoebe) has been fully confirmed, and a
tenth satellite discovered.

1 Pop. Asi., vol. 12, pp. 408-9.

CHAPTER X

Uranus and Neptune

FROM observations of Uranus made in 1896,
M. Leo Brenner concluded that the planet
rotates on its axis in about 8^ hours
(probably 8h 27m). This is a short period, but
considering the short periods of Jupiter and
Saturn there seems to be nothing improbable
about it.

Prof. Barnard finds that the two inner
satellites of Uranus are difficult objects even
with the great 36-inch telescope of the Lick
Observatory ! They have, however, been photo-
graphed at Cambridge (U.S.A.) with a 13-inch
lens, although they are " among the most difficult
objects known." l

Sir William Huggins in 1871 found strong
absorption lines (six strong lines) in the spectrum
of Uranus. One of these lines indicated the
presence of hydrogen, a gas which does not exist
in our atmosphere. Three of the other lines seen
were situated near lines in the spectrum of
atmospheric air. Neither carbonic acid nor sodhim
1 Nature, August 29, 1889.

92 ASTRONOMICAL CURIOSITIES

showed any indications of their presence in the
planet's spectrum. A photograph by Prof. Slipher
of Neptune's spectrum " shows the spectrum of
this planet to contain many strong absorption
bands. These bands are so pronounced in the part
of the spectrum between the Fraunhofer lines
F and D, as to leave the solar spectrum unrecog-
nizable. . . . Neptune's spectrum is strikingly
different from that of Uranus, the bands in the
latter planet all being reinforced in Neptune. In
this planet there are also new bands which have
not been observed in any of the other planets.
The F line of hydrogen is remarkably dark . . .
this band is of more than solar strength in the
spectrum of Uranus also. Thus free hydrogen
seems to be present in the atmosphere of both
these planets. This and the other dark bands
in these planets bear evidence of an enveloping
atmosphere of gases which is quite unlike that
which surrounds the earth." l

With the 18-inch equatorial telescope of the
Strasburgh Observatory, M. Wirtz measured the
diameter of Neptune, and found from forty-nine
measures made between December 9, 1902, and
March 28, 1903, a value of 2"'303 at a distance of
30*1093 (earth's distance from sun = l). This given
a diameter of 50,251 kilometres, or about 31,225
miles,2 and a mean density of 1*54 (water=l;

1 Attrophysical Journal, vol. 2G (1907), p. 62.

2 Bulletin, A*t. Soc.de France, January, 1904.

URANUS AND NEPTUNE 93

earth's mean density = 5'53). Prof. Barnard's
measures gave a diameter of 32,900 miles, a
fairly close agreement, considering the difficulty
of measuring so small a disc as that shown by
Neptune.

The satellite of Neptune was photographed at
the Pulkown Observatory in the year 1899. The
name Triton has been suggested for it. In the
old Greek mythology Triton was a son of Neptune,
so the name would be an appropriate one.

The existence of a second satellite of Neptune
is suspected by Prof. Schaeberle, who thinks he
once saw it with the 36-inch telescope of the Lick
Observatory "on an exceptionally fine night " iii
1895.1 But this supposed discovery has not yet
been confirmed. Lassell also thought he had
discovered a second satellite, but this supposed
discovery was never confirmed.1

The ancient Burmese mention eight planets, the
sun, the moon, Mercury, Venus, Mars, Jupiter,
Saturn, and another named Rahu, which is in-
visible. It has been surmised that " Rahu " is
Uranus, which, is just visible to the naked eye,
and may possibly have been discovered by keen
eyesight in ancient times. The present writer has
seen it several times without optical aid in the
West of Ireland, and with a binocular field- glass
of 2 inches aperture he found it quite a con-
spicuous object.

1 Humboldt'g Cosmos, vol. iv. p. 532.

94 ASTRONOMICAL CURIOSITIES

When Neptune was visually discovered by
Galle, at Berlin, he was assisted in his observa-
tion by Prof, d' Arrest. The incident is thus de-
scribed by Dr. Dreyer, " On the night of June 14,
1874, while observing Coggia's comet together,
I reminded Prof, d' Arrest how he had once said in
the course of a lecture, that he had been present
at the finding of Neptune, and that * he might say
it would not have been found without him.' He
then told me (and I wrote it down the next day),
how he had suggested the use of Bremiker's map
(as first mentioned by Dr. Galle in 1877) and con-
tinued, * We then went back to the dome, where
there was a kind of desk, at which I placed myself
with the map, while Galle, looking through the
refractor, described the configurations of the stars
he saw. I followed them on the map one by one,
until he said : " And then there is a star of the
8th magnitude, in such and such a position,"
whereupon I immediately exclaimed : " That star
is not on the map," ' x This was the planet. But
it seems to the present writer that if Galle or
d' Arrest had access to Harding's Atlas (as they
probably had) they might easily have found the
planet with a good binocular field-glass. As a
matter of fact Neptune is shown in Harding's
Atlas (1822) as a star of the 8th magnitude,
having been mistaken for a star by Lalande on
May 8 and 10, 1795 ; and the present writer has
1 Copernicus, vol. ii. p. 64.

URANUS AND NEPTUNE 95

found Harding's 8th magnitude stars quite easy
objects with a binocular field- glass having object-
glasses of two inches diameter, and a power of
about six diameters.

SUPPOSED PLANET BEYOND NEPTUNE. — The
possible existence of a planet beyond Neptune
has been frequently suggested. From considera-
tions on the aphelia of certain comets, Prof. Forces
in 1880 computed the probable position of such a
body. He thought this hypothetical planet would
be considerably larger than Jupiter, and probably
revolve round the sun at a distance of about 100
times the earth's mean distance from the sun.
The place indicated was between R.A. llh 24m and
12h 12m, and declination 0° 0' to 6° 0' north. With a
view to its discovery, the late Dr. Roberts took a
series of eighteen photographs covering the region
indicated. The result of an examination of these
photographs showed, Dr. Roberts says, that " no
planet of greater brightness than a star of the
1 5th magnitude exists on the sky area herein
indicated." Prof. W. H. Pickering has recently
revived the question, and has arrived at the
following results : Mean distance of the planet
from the sun, 51'0 (earth's mean distance = 1);
period of revolution, 373J years ; mass about
twice the earth's mass ; probable position for
1909 about R.A. 7h 47m, north declination 21°,
or about 5° south-east of the star * Geminorum.
The supposed planet would be faint, its brightness

96 ASTRONOMICAL CURIOSITIES

being from 11 J to 13J, according to the " albedo"
(or reflecting power) it may have.1

Prof. Forbes has again attacked the question of
a possible ultra-Neptunian planet, and from a
consideration of the comets of 1556, 1843 I, 1880 I,
and 1882 II, finds a mean distance of 105*4, with
an inclination of the orbit of 52° to the plane of
the ecliptic. This high inclination implies that
"during the greatest part of its revolution it is
beyond the zodiac," and this, Mr. W. T. Lynn
thinks, "may partly account for its not having
hitherto been found by observation.2

From a consideration of the approximately
circular shape of the orbits of all the large planets
of the solar system, Dr. See suggests the existence
of three planets outside Neptune, with approxi-
mate distances from the sun of 42, 56, and 72
respectively (earth's distance = 1), and recommends
a photographic search for them. He says, "To
suppose the planetary system to terminate with
an orbit so round as that of Neptune is as absurd
as to suppose that Jupiter's system terminates
with the orbit of the fourth satellite." 3

According to Grant, even twenty years before
the discovery of Neptune the error of Prof.
Adams' first approximation amounted to little
more than 10°.4

1 Knowledge, May, 1909.

2 Journal, British Astronomical Association, January, 1909,
p. 132.

3 Ast. Nach., No. 4308. 4 History of Physical Astronomy, p, 204.

CHAPTER XI

Comets

WE learn from Pliny that comets were
classified in ancient times, according
to their peculiar forms, into twelve
classes, of which the principal were : Pogonias,
bearded ; Lampadias, torch-like ; Xiphias, sword-
like ; Pitheus, tun-like ; Acontias, javelin-like ;
Ceratias, horn-like ; Disceus, quoit-like ; and Hip-
pias, horse-mane-like.1

Of the numerous comets mentioned in astrono-
mical records, comparatively few have been visible
to the naked eye. Before the invention of the tele-
scope (1610) only those which were so visible could,
of course, be recorded. These number about 400.
Of the 400 observed since then, some 70 or 80 only
have been visible by unaided vision ; and most of
these now recorded could never have been seen
without a telescope. During the last century, out
of 300 comets discovered, only 13 were very visible
to the naked eye. Hence, when we read in the
newspapers that a comet has been discovered the

1 Smyth's Celestial Cycle, pp. 210, 211.

98 ASTRONOMICAL CURIOSITIES

chances are greatly against it becoming visible to
the naked eye.1

Although comparatively few comets can be seen
without a telescope, they are sometimes bright
enough to be visible in daylight ! Such were those
of B.C. 43, A.D. 1106, 1402, 1532, 1577, 1744, 1843,
and the " great September comet " of 1882.

If we except the great comet of 1861, through the
tail of which the earth is supposed to have passed,
the comet which came nearest to the earth was
that of 1770, known as Lexell's, which approached
us within two millions of miles, moving nearly in
the plane of the ecliptic. It produced, however,
no effect on the tides, nor on the moon's motion,
which shows that its mass must have been very
small. It was computed by Laplace that if its
mass had equalled that of the earth, the length of
our year would have been shortened by 2 hours
47 minutes, and as there was no perceptible
change Laplace concluded that the comet's mass
did not exceed ^otn of tne earth's mass. This is
the comet which passed so near to Jupiter that
its period was reduced to 5J years. Owing to
another near approach in 1779 it became invisible
from the earth, and is now lost.2 Its identity with
the recently discovered eighth satellite of Jupiter
has been suggested by Mr. George Forbes (see under
" Jupiter "). At the near approach of Lexell's comet
to the earth in 1770, Messier, " the comet ferret,

1 Poor, The Solar System,?. 274. « Celestial Cycle, p. 246.

COMETS 99

found that its head had an apparent diameter of
2J°, or nearly five times that of the moon !

Another case^of near approach to the earth was
that of Biela's comet at its appearance in 1805.
On the evening of December 9 of that year, the
comet approached the earth within 3,380,000
miles.1

The comet of A.D. 1106 is stated to have been
seen in daylight close to the sun. This was on
February 4 of that year. On February 10 it had
a tail of 60° in length, according to Gaubil.2

The comet of 1577 seems to have been one of the
brightest on record. According to Tycho Brahe,
it was visible in broad daylight. He describes the
head as " round, bright, and of a yellowish light,"
with a curved tail of a reddish colour.3

The comet of 1652 was observed for about three
weeks only, and Hevelius and Comiers state that
it was equal to the moon in apparent size ! This
would indicate a near approach to the earth. An
orbit computed by Halley shows that the least
distance was about 12 millions of miles, and the
diameter of the comet's head rather less than
110,000 miles, or about 14 times the earth's
diameter.

According to Mr. Denning, " most of the
periodical comets at perihelion are outside the
earth's orbit, and hence it follows that they escape

1 Nature, October 2, 1879. 2 Ibid., May 6, 1880.

3 Ibid., February 19, 1880.

100 ASTRONOMICAL CURIOSITIES

observation unless the earth is on the same side of
the sun as the comet." l

It was computed by M. Faye that the volume
of the famous Donati's comet (1858) was about
500 times that of the sun ! On the other hand, he
calculated that its mass (or quantity of matter it
contained) was only a fraction of the earth's mass.
This shows how almost inconceivably tenuous the
material forming the comet must have been —
much more rarefied, indeed, than the most perfect
vacuum which can be produced in an air-pump.
This tenuity is shown by the fact that stars were
seen through the tail "as if the tail did not
exist." A mist of a few hundred yards in thick-
ness is sufficient to hide the stars from our view,
while a thickness of thousands of miles of comet-
ary matter does not suffice even to dim their
brilliancy !

At the time of the appearance of the great
comet of 1843, it was doubtful whether the comet
had transited the sun's disc. But it is now known,
from careful calculations by Prof. Hubbard, that
a transit really took place between llh 28m and
12h 29m on February 27, 1843, and might have been
observed in the southern hemisphere. The dis-
tance of this remarkable comet from the sun at
its perihelion passage was less than that of any
known comet. A little before 10 p.m. on Feb-
ruary 27, the comet passed within 81,500 miles of
1 Nature, September 30, 1897.

COMETS 101

the sun's surface with the enormous velocity of
348 miles a second ! It remained less than 2£ hours
north of the ecliptic, passing from the ascending
to the descending node of its orbit in 2h 13m*4.1
The great comet of 1882 transited the sun's disc
on Sunday, September 17, of that year, the ingress
taking place at 4h 50m 58s, Cape mean time. When
on the sun the comet was absolutely invisible,
showing that there was nothing solid about it. It
was visible near the sun with the naked eye a
little before the transit took place.2 This great
comet was found by several computers to have
been travelling in an elliptic orbit with a period
of about eight centuries. Morrison found 712
years ; Frisby, 794 ; Fabritius, 823 ; and Kreutz,
843 years.3

The great southern comet of 1887 may be de-
scribed as a comet without a head ! The popular
idea of a comet is a star with a tail. But in this
case there was no head visible — to the naked eye
at least. Dr. Thome of the Cordoba Observatory
— its discoverer — describes it as " a beautiful object
— a narrow, straight, sharply denned, graceful
tail, over 40° long, shining with a soft starry light
against a dark sky, beginning apparently without
a head, and gradually widening and fading as it
extended upwards." 4

1 Nature, August 5, 1875.

2 IMd., October 12, 1882, and Copernicus, vol. iii. p. 85.

3 Nature, May 8, 1881. 4 Ibid, June 16, 1887.

102 ASTRONOMICAL CURIOSITIES

The great southern comet of 1901 had five tails
on May 6 of that year. Two were fairly bright,
and the remaining three rather faint. Mr. Gale
saw a number of faint stars through the tails.
The light of these seem to have been "undim-
med." Mr. Cobham noticed that the stars Rigel
and /5 Eridani shone through one of the faint tails,
and " showed no perceptible difference." *

Prof. W. H. Pickering says that " the head of a
comet, as far as our present knowledge is con-
cerned, seems therefore to be merely a meteor
swarm containing so much gaseous material that
when electrified by its approach to the sun it will
be rendered luminous" (Harvard Annual, vol.
xxxii. part ii. p. 295) "... if the meteors and their
atmospheres are sufficiently widely separated f rom
one another, the comet may be brilliant and yet
transparent at the same time."

In the case of Swift's comet of 1892 some
periodical differences of appearance were due,
according to Prof. W. H. Pickering, to a rotation
of the comet round an axis passing longitudinally
through the tail, and he estimated the period of
rotation at about 94 to 97 hours. He computed
that in this comet the repulsive force exerted by
the sun on the comet's tail was " about 39' 5 times
the gravitational force." 2

The comet known as 19026 approached the

1 Journal, B.A.A., December 13, 1901.

2 Nature, September 20, 1900.

UNIVERSITY

COMETS 103

planet Mercury within two millions of miles on
November 29 of that year. Prof. O. C. Wendell, of
Harvard Observatory, made some observations on
the transparency of this comet. He found with
the aid of a photometer and the 15-inch telescope
of the observatory that in the case of two faint
stars over which the comet passed on October 14,
1902, the absorption of light by the comet was
insensible, and possibly did not exceed one or
two hundredths of a magnitude,1 an amount quite
imperceptible to the naked eye, and shows con-
clusively how almost inconceivably rarefied the
substance of this comet must be.

The comet known as Morehouse (1908c) showed
some curious and wonderful changes. Mr. Borelly
found that five tails are visible on a photographic
plate taken on October 3, 1908, and the trail of an
occulted star indicates a slight absorption effect.
According to M. L. Rabourdin, great changes
took place from day to day, and even during the
course of an hour ! Similar changes were recorded
by G. M. Gauthier; and Prof. Barnard, who
photographed the comet on 30 nights from
September 2 to October 13, states that the photo-
graphs of September 30 "are unique, whilst the
transformation which took place between the
taking of these and the taking of the next one on
October 1 was very wonderful." • The spectrum

1 Ast. Nach., No. 3868, and Nature, March 12, 1903.

2 Nature, November 13, 1908.

10* ASTRONOMICAL CURIOSITIES

showed the lines of cyanogen instead of the
hydrocarbon spectrum shown by most comets.

Prof. Barnard has suggested that all the
phenomena of comets' tails cannot be explained
by a repulsive force from the sun. Short tails
issuing from the comet's nucleus at considerable
angles with the main tail point to eruptive action
in the comet itself. The rapid changes and dis-
tortions frequently observed in the tails of some
comets suggest motion through a resisting
medium ; and the sudden increase of light also
occasionally observed points in the same
direction.1

It was computed by Olbers that if a comet
having a mass of j^^h of the earth's mass — which
would form a globe of about 520 miles in diameter
and of the density of granite — collided with the
earth, with a velocity of 40 miles a second, our
globe would be shattered into fragments.2 But
that any comet has a solid nucleus of this size
seems very doubtful; and we may further say
that the collision of the earth with any comet is
highly improbable.

It seems to be a common idea that harvests are
affected by comets, and even " comet wines " are
sometimes spoken of. But we know that the
earth receives practically no heat from the
brightest comet. Even in the case of the brilliant
comet of 1811, one of the finest on record, it was

1 Nature, December 7, 1905. 2 Celestial Cycle, p. 259.

COMETS 105

found that " all the efforts to concentrate its
rays did not produce the slightest effect on the
blackened bulb of the most sensitive thermometer."
Arago found that the year 1808, in which several
comets were visible, was a cold year, "and 1831,
in which there was no comet, enjoyed a much
higher temperature than 1819, when there were
three comets, one of which was very brilliant." 1
We may, therefore, safely conclude that even a
large comet has no effect whatever on the
weather.

From calculations on the orbit of Halley's
comet, the next return of which is due in 1910,
Messrs. Cowell and Crommelin find that the
identity of the comet shown on the Bayeux
Tapestry with Halley's comet is now " fully
established." They find that the date of perihelion
passage was March 25, 1066, which differs by only
4 days from the date found by Hind. The im-
posing aspect of the comet in 1066 described in
European chronicles of that time is confirmed by
the Chinese Annals. In the latter records the
brightness is compared to that of Venus, and
even with that of the moon ! The comparison
with the moon was probably an exaggeration, but
the comet doubtless made a very brilliant show.
In the Bayeux Tapestry the inscription on the
wall behind the spectators reads: "isti mirant
stella." Now, this is bad Latin, and Mr. W. T.
1 Celestial Cycle, p. 260.

106 ASTRONOMICAL CURIOSITIES

Lynn has made the interesting suggestion that
some of the letters are hidden by the buildings in
front and that the real sentence is " isti mirantur
stellam." 1 The present writer has examined the
copy of the Bayeux Tapestry which is in the
Dublin Museum, and thinks that Mr. Lynn's
suggestion seems very plausible. But the last
letter of stellam is apparently hidden by the
comet's tail, which does not seem very probable !

The conditions under which the comet will
appear in 1910 are not unlike those of 1066 and
1145. " In each year the comet was discovered as
a morning star, then lost in the sun's rays ; on its
emergence it was near the earth and moved
with great rapidity, finally becoming stationary
in the neighbourhood of Hydra, where it was lost
to view." 2 In 1910 it will probably be an evening
star before March 17, and after May 11, making a
near approach to the earth about May 12. About
this time its apparent motion in the sky will be
very rapid. As, however, periodical comets — such
as Halley's — seem to become fainter at each
return, great expectations with reference to its
appearance in 1910 should not be indulged in.

The appearance of Halley's comet in A.D. 1222 is
thus described by Pingre— a great authority on
comets — (quoting from an ancient writer) —
" In autumn, that is to say in the months of

> Journal, B.A.A., April, 1907.

2 Monthly Notices, R.A.S., March, 1908.

COMETS 107

August andSeptember,'a star of the first magnitude
was seen, very red, and accompanied by a great tail
which extended towards the top of the sky in the
form of a cone extremely pointed. It appeared to
be very near the earth. It was observed (at
first ?) near the place of the setting sun in the
month of December."

With reference to its appearance in the year
1456, when it was of " vivid brightness," and had
a tail of 60° in length, Admiral Smyth says,1 " To
its malign influence were imputed the rapid
successes of Mahomet II., which then threatened
all Christendom. The general alarm was greatly
aggravated by the conduct of Pope Callixtus III.,
who, though otherwise a man of abilities, was a
poor astronomer; for that pontiff daily ordered
the church bells to be rung at noon-tide, extra
Ave-Marias to be repeated, and a special protest
and excommunication was composed, exorcising
equally the Devil, the Turks, and the comet."
With reference to this story, Mr. G. F. Chambers
points out2 that it is probably based on a pas-
sage in Platina's Vitce Pontificum. But in this
passage there is no mention made of excommuni-
cation or exorcism, so that the story, which has
long been current, is probably mythical. In con-
firmation of this view, the Rev. W. F. Rigge has
shown conclusively 3 that no bull was ever issued

1 Celestial Cycle, p. 231.

2 Journal, B.A.A., July, 1908.

3 Popular Agronomy, October, 1908.

108 ASTRONOMICAL CURIOSITIES

by Pope Callixtus III. containing a reference to
any comet. The story would therefore seem to be
absolutely without foundation, and should be
consigned to the limbo of all such baseless myths.
With reference to the appearance of Halley's
comet, at his last return in 1835, Sir John
Herschel, who observed it at the Cape of Good
Hope, says —

"Among the innumerable stars of all magni-
tudes, from the ninth downwards, which at
various times were seen through it, and some
extremely near to the nucleus (though not exactly
on it) there never appeared the least ground for
presuming any extinction of their light in traver-
sing it. Very minute stars indeed, on entering
its brightest portions, were obliterated, as they
would have been by an equal illumination of the
field of view ; but stars which before their entry
appeared bright enough to bear that degree of
illumination, were in no case, so far as I could
judge, affected to a greater extent than they
would have been by so much lamp-light artificially
introduced."1

It is computed by Prof. J. ^Holetschak that,
early in October, 1909, Halley's comet should have
the brightness of a star of about 14^ magnitude.3
It should then — if not detected before — be dis-
coverable with some of the large telescopes now
available.

According to the computations of Messrs. Cowell
and Crommelin, the comet should enter Pisces

> Cape O&a., p. 401. 2 Nature, July 2, 1908.

COMETS 109

from Aries in January, 1910. "Travelling west-
ward towards the star y Piscium until the begin-
ning of May, and then turning eastward again, it
will travel back through the constellations Cetus,
Orion, Monoceres, Hydra, and Sextans." From
this it seems that observers in the southern
hemisphere will have a better view of the comet
than those in northern latitudes. The computed
brightness varies from 1 on January 2, 1910, to
1112 on May 10. But the actual brightness of
a comet does not always agree with theory. It
is sometimes brighter than calculation would
indicate.

According to Prof. O. C. Wendell, Halley's
comet will, on May 12, 1910, approach the earth's
orbit within 4*6 millions of miles ; and he thinks
that possibly the earth may " encounter some
meteors," which are presumably connected with
the comet. He has computed the " radiant point "
of these meteors (that is, the point from which
they appear to come), and finds its position to be
R.A. 22h 42m-9, Decl. N. 1° 18'. This point lies a
little south-west of the star /3 Piscium.

According to Dr. Smart, the comet will, on
June 2, " cross the Equator thirteen degrees south
of Regulus, and will then move slowly in the
direction of </> Leonis. The comet will be at its
descending node on the ecliptic in the morning
of May 16, and the earth will pass through the
node on the comet's orbit about two and a half

110 ASTRONOMICAL CURIOSITIES

days later. The comet's orbit at the node is
about 13 million miles within that of the earth.
Matter repelled from the comet's nucleus by the
sun with a velocity of about 216,000 miles per
hour, would just meet the earth when crossing
the comet's orbit plane. Matter expelled with a
velocity of 80,000 miles per hour, as in the case
of Comet Morehouse, would require seven days
for the journey. Cometary matter is said to
have acquired greater velocities than this, for
(according to Webb, who quotes Chacornac)
Comet II., 1862, shot luminous matter towards
the sun, with a velocity of nearly 2200 miles per
second. It is therefore possible that matter
thrown off by the comet at the node may enter
our atmosphere, in which case we must hope that
cyanogen, which so often appears in cometary
spectra, may not be inconveniently in evidence." 1

Cyanogen is, of course, a poisonous gas, but
cometary matter is so rarefied that injurious
effects on the earth need not be feared.

If we can believe the accounts which have been
handed down to us, some very wonderful comets
were visible in ancient times. The following may
be mentioned : —

B.C. 165. The sun is said to have been "seen
for several hours in the night." If this was a comet
it must have been one of extraordinary brilliancy.2

1 Journal, B.A.A., January 20, 1909, pp. 123-4.

2 Chambers' Hanrtbooli of Astronomy, Catalogue of Cometa.

COMETS 111

B.C. 146. " After the death of Demetrius, king
of Syria, the father of Demetrius and Antiochus,
a little before the war in Achaia, there appeared
a comet as large as the sun. Its disc was first
red, and like fire, -spreading sufficient light to
dissipate the darkness of night; after a little
while its size diminished, its brilliancy became
weakened, and at length it entirely disappeared." l

B.C. 134. It is recorded that at the birth of
Mithridates a great comet appeared which
"occupied the fourth part of the sky, and its
brilliancy was superior to that of the sun." (?) 2

B.C. 75. A comet is described as equal in size
to the moon, and giving as much light as the sun
on a cloudy day. (!) 3

A.D. 531. In this year a great comet was
observed in Europe and China. It is described
as " a very large and fearful comet," and was
visible in the west for three weeks. Hind thinks
that this was an appearance of Halley's comet,4
and this has been confirmed by Mr. Crommelin.

A.D. 813, August 4. A comet is said to have
appeared on this date, of which the following
curious description is given: "It resembled two
moons joined together ; they separated, and
having taken different forms, at length appeared
like a man without a head." (!) 5

1 Seneca, quoted by Chambers, Handbook, voL i. p. 554
(Fourth Edition).

2 Ibid. 3 Hid. * Ibid,, p. 534. 3 Ibid.

ASTRONOMICAL CURIOSITIES

A.D. 893. A great comet is said to have
appeared in this year with a tail 100° in length,
which afterwards increased to 200° ! l

A.D. 1402. A comet appeared in February of
this year, which was visible in' daylight for eight
days. " On Palm Sunday, March 19, its size was
prodigious." Another comet, visible in the day-
time, was seen from June to September of the
same year.

When the orbit of the comet known as 1889 V
was computed, it was found that it had passed
through Jupiter's system in 1886 (July 18-21).
The calculations show that it must have passed
within a distance of 112,300 miles of the planet
itself — or less than half the moon's distance from
the earth — and " its centre may possibly have
grazed the surface of Jupiter." 2

Sir John Herschel thought that the great comet
of 1861 was by far the brightest comet he had
ever seen, those of 1811 and 1858 (Donati's) not
excepted.3 Prof. Kreutz found its period of revo-
lution round the sun to be about 409 years, with
the plane of the orbit nearly at right angles to
the plane of the ecliptic.

On November 9, 1795, Sir William Herschel
saw the comet of that year pass centrally over

1 Ma-tuoan-lin, quoted by Chambers, Handbook, p. 570.

2 Astronomy and Astrophysics, 1893, p. 798.

3 TJte Observatory, October, 1898.

COMETS 113

a small double star of the llth and 12th
magnitudes, and the fainter of the two com-
ponents remained distinctly visible during the
comet's transit over the star. This comet' was
an appearance of the comet now known as
Encke's.1 Struve saw a star of the 10th magni-
tude through nearly the brightest part of Encke's
comet on November 7, 1828, but the star's light
was not dimmed by the comet.

Sir John Herschel saw a cluster of stars of
the 16th or 17th magnitude through Biela's
comet, although the interposed cometary matter
must have been at least 50,000 miles in thickness.2

Bessel found that on September 29, 1835, a star
of the 10th magnitude shone with undimmed
lustre through the tail of Halley's comet within
8 seconds of arc of the central point of the head.
At Dorpat (Russia) Struve saw the same star " in
conjunction only 2""2 from the brightest point of
the comet. The star remained continuously
visible, and its light was not perceptibly diminished
whilst the nucleus of the comet seemed to be
almost extinguished before the radiance of the
small star of the 9th or 10th magnitude." 3

Webb says —

" Donati saw a 7 mg. star enlarged so as to show
a sensible disc, when the nucleus of comet III.,

1 Grant's History of Physical Astronomy, p. 293.

2 Ibid., p. 294.

3 Humboldt's Cosmos, vol. i. pp. 89, 90 (Otte's translation).

114 ASTRONOMICAL CURIOSITIES

1860, passed very near it. Stars are said to
have started, or become tremulous, during occulta-
tions by comets. Birmingham observed the comet
of Encke illuminated by a star over which it
passed, August 23, 1868; and Klein, in 1861,
remarked an exceptional twinkling in 5 mg. stars
involved in the tail." l

The comet of 1729 had the greatest perihelion
distance of any known comet ; 2 that is, when
nearest to the sun, it did not approach the
central luminary ;within four times the earth's
distance from the sun I

Barnard's comet, 1889 I., although it never
became visible to the naked eye, was visible with
a telescope from September 2, 1888, to August 18,
1890, or 715 days — the longest period of visibility
of any comet on record. When last seen it was
65 times the earth's distance from the sun, or
about 580 millions of miles, 3 or beyond the orbit
of Jupiter !

Messier, who was called " the comet ferret,"
discovered " all his comets with a small 2-foot
telescope of 2J inches aperture, magnifying 5
times, and with a field of 4°." 4

It is a very curious fact that Sir William
Herschel, " during all his star-gaugings and sweeps
for nebulae, never discovered a comet ; " 5 that is

1 Celestial Objects, vol. i. p. 211, footnote.

2 Denning, Telescopic Work far Starlight Evenings, p. 248.
» Ibid., p. 248.

4 Ibid., p. 250. * Ibid., p. 231.

COMETS 115

an object which was afterwards proved to be a
comet. Possibly, however, some of his nebulae
which are now missing, may have been really
comets.

Sir William Herschel found the diameter of the
head of the great comet of 1811 to be 127,000
miles. The surrounding envelope he estimated to
be at least 643,000 miles, or about three-fourths
of the sun's diameter.

On a drawing of the tails of the great comet
of 1744 given in a little book printed in Berlin
in that year, no less than 12 tails are shown !
These vary in length and brightness. A copy
of this drawing is given in Copernicus.1 The
observations were made by " einen geschichten
Frauenzimmer," who Dr. Dreyer identifies with
Christian Kirch, or one of her two sisters,
daughters of the famous Gottfried and Maria
Margaretta Kirch (Idem, p. 107). Dr. Dreyer
thinks that the drawing " seems to have been
carefully made, and not to be a mere rough sketch
as I had at first supposed " (Idem, p. 185).

The tails of some comets were of immense
length. That of the comet of 1769 had an absolute
length of 38 millions of miles. That of 1680, 96
million of miles, or more than the sun's distance
from the earth. According to Sir William
Herschel, the tail of the great comet of 1811 was
over 100 millions of miles in length. That of the
1 Vol. iii. p. 106.

116 ASTRONOMICAL CURIOSITIES

great comet of 1843 — one of the finest in history —
is supposed to have reached a length of 150
millions of miles ! l

In width the tails of comets were in some cases
enormous. According to Sir William Herschel,
the tail of the comet of 1811 had a diameter of
15 millions of miles I Its volume was, therefore,
far greater than that of the sun ! l

According to Hevelius the comet of 1652 was
of such a magnitude that it " resembled the moon
when half full ; only it shone with a pale and
dismal light." 2

Halley's comet at its next appearance will be
examined with the spectroscope for the first time
in its history. At its last return in 1835, the
spectroscope had not been invented.

For the great comet of 1811, Arago computed
a period of 3065 years ; and Eiicke found a period
of 8800 years for the great comet of 1680.3

The variation in the orbital velocity of some
comets is enormous. The velocity of the comet
of 1680 when passing round the sun (perihelion)
was about 212 miles a second ! Whereas at its
greatest distance from the sun (aphelion) the
velocity is reduced to about 10 feet a second !

1 Grant's History of Physical Astronomy, p. 298.

8 Ibid., p. 305.

3 Humboldt's Cosmos, vol. i. p. 95.

CHAPTER XII

Meteors

MR. DENNING thinks that the meteor
shower of the month of May, known
as the Aquarids, is probably connected
with Halley's comet. The meteors should be
looked for after 1 a.m. during the first week in
May, and may possibly show an enhanced display
in May, 1910, when Halley's comet will be near
the sun and earth.1

On November 29, 1905, Sir David Gill observed
a fireball with an apparent diameter equal to
that of the moon, which remained visible for 5
minutes and disappeared in a hazy sky. Observed
from another place, Mr. Fuller found that the
meteor was visible 2 hours later! Sir David
Gill stated that he does not know of any similar
phenomenon. 2

Mr. Denning finds that swiftly moving meteors
become visible at a greater height above the
earth's surface than the slower ones. Thus, for
the Leonids and Perseicls, which are both swift,

1 Nature, April 30, 1908.

2 Bulletin, AsL Soc. de France, Mny, 190G.

118 ASTRONOMICAL CURIOSITIES

it has been found that the Leonids appear at an
average height of 84 miles, and disappear at a
height of 56 miles ; and the Perseids at 80 and 54
miles respectively. " On the other hand, the mean
height of the very slow meteors average about
65 miles at the beginning and 38 miles at the end
of their appearance." 2

During the night of July 21-22, 1896, Mr.
William Brooks, the well-known, astronomer, and
director of the Smith Observatory at Geneva
(New York), saw a round dark body pass slowly
across the moon's bright disc, the moon being
nearly full at the time. The apparent diameter
of the object was about one minute of arc, and
the duration of the transit 3 or 4 seconds, the
direction of motion being from east to west. On
August 22 of the same year, Mr Gathman (an
American observer) saw a meteor crossing the
sun's disc, the transit lasting about 8 seconds.2

A meteor which appeared in Italy on July 7,
1892, was shown by Prof, von Niessl to have had
an ascending path towards the latter end of its
course ! The length of its path was computed to
be 683 miles. When first seen, its height above
the earth was about 42 miles, and when it dis-
appeared its height had increased to about 98
miles, showing that its motion was directed
upwards ! 3

1 Nature, November 24, 1904. - Ibid., September 10, 189C.

3 Ibi<l, June 29, 18IKJ.

METEORS 119

In the case of the fall of meteoric stones, which
occasionally occur, it has sometimes been noticed
that the sound caused by the explosion of the
meteorite, or its passage through the air, is heard
before the meteorite is seen to fall. This has
been explained by the fact that owing to the
resistance of the air to a body moving at first
with a high velocity its speed is so reduced that it
strikes the earth with a velocity less than that of
sound. Hence the sound reaches the earth before
the body strikes the ground.1

The largest meteoric stone preserved in a
museum is that known as the Anighita, which
weighs 36^ tons, and was found at 'Cape York in
Greenland. It was brought to the American
Museum of Natural History by Commander R. E.
Peary, the Arctic explorer.

The second largest known is that of Bacubirito
in Mexico, the weight of which is estimated at
27J tons.

The third largest is that known as the
Willianiette, which was found in 1902 near the
town of that name in Western Oregon (U.S.A.).
It is composed of metallic nickel-iron, and weighs
about 13^ tons. It is now in the American
Museum of Natural History.

A large meteorite was actually seen, from the
deck of the steamer African Prince, to fall into the
Atlantic Ocean, on October 7, 1906! The captain
1 Journal, B.A.A., May 22, 1903.

120 ASTRONOMICAL CURIOSITIES

of the vessel, Captain Anderson, describes it as
having a train of light resembling " an immense
broad electric-coloured band, gradually turning
to orange, and then to the colour of molten
metal. When the meteor came into the denser
atmosphere close to the earth, it appeared, as
nearly as is possible to describe it, like a molten
mass of metal being poured out. It entered the
water with a hissing noise close to the ship." l
This was a very curious and perhaps unique
phenomenon, and it would seem that the vessel
had a narrow escape from destruction.

In Central Arizona (U.S.A.) there is a hill called
Coon Butte, or Coon Mountain. This so-called
" mountain " rises to a height of only 130 to 160
feet above the surrounding plain, and has on its
top a crater of 530 to 560 feet deep ; the bottom
of the crater — which is dry — being thus 400 feet
below the level of the surrounding country. This
so-called " crater " is almost circular and nearly
three-quarters of a mile in diameter. It has been
suggested that this " crater " was formed by the
fall of an enormous iron meteorite, or small
asteroid. The " crater " has been carefully
examined by a geologist and a physicist. From
the evidence and facts found, the geologist
(Mr. Barringer) states that " they do not leave,
in my mind, a scintilla of doubt that this moun-
tain and its crater were produced by the impact
1 Nature, December 13, 1906, p. 159.

METEORS 121

of a huge meteorite or small asteroid." The
physicist (Mr. Tilglmiann) says that he "is
justified, under due reserve as to subsequently
developed facts, in announcing that the formation
at this locality is due to the impact of a meteor
of enormous and unprecedented size." There are
numerous masses of meteoric iron in the vicinity
of the " crater." The so-called Canyon Diabolo
meteorite was found in a canyon of that name
about 2J miles from the Coon Mountain. The
investigators estimate that the great meteoric
fall took place " not more than 5000 years ago,
perhaps much less." Cedar trees about 700 years
old are now growing 011 the rim of the mountain.
From the results of artillery experiments, Mr.
Gilbert finds that " a spherical projectile striking
solid limestone with a velocity of 1800 feet a
second will penetrate to a depth of something less
than two diameters,' and from this Mr. L.
Fletcher concludes "that a meteorite of large
size would not be prevented by the earth's
atmosphere from having a penetration effect
sufficient for the production of such a crater." *

The meteoric origin of this remarkable
" crater " is strongly favoured by Mr. G. P. Merrill,
Head Curator of Geology, U.S. National Museum.

The Canyon Diabolo meteorite above referred to
was found to contain diamonds ! some black,
others transparent. So some have said that " the
1 Nature, September 13, 190G.

ASTRONOMICAL CURIOSITIES

diamond is a gift from Heaven," conveyed to
earth in meteoric showers.1 But diamond-
bearing meteorites would seem to be rather a
freak of nature. It does not follow that all
diamonds had their origin in meteoric stones.
The mineral known as periodot is frequently found
in meteoric stones, but it is also a constituent of
terrestrial rocks.

In the year 1882 it was stated by Dr. Halm and
Dr. Weinhand that they had found fossil sponges,
corals, and crinoids in meteoric stones ! Dr. Wein-
hand thought he had actually determined three
genera ! 2 But this startling result was flatly
contradicted by Carl Vogt, who stated that the
supposed fossils are merely crystalline conforma-
tions.3

Some meteorites contain a large quantity of
occluded gases, hydrogen, helium, and carbon
oxides. It is stated that Dr. Odling once " lighted
up the theatre of .the Royal Institution with
gas brought down from interstellar space by
meteorites " 1 4

On February 10, 1896, a large meteorite burst
over Madrid with a loud report. The concussion
was so great that many windows in the city
were broken, and some partitions in houses
were shaken down ! 5

1 Nature, October 12, 1905, p. 596.

2 Knowledge, January 13, 1882. 3 Ibid., January 20, 1882,
4 Popular Astronomy, June- July, 1908, p. 345.

4 The Observatory, March, 189C, p. 135.

METEORS

A very brilliant meteor or fireball was seen in
daylight on June 9, 1900, at 2h 55ra p.m. from
various places in Surrey, Sussex, and near London.
Calculations showed that " the meteor began 59
miles in height over a point 10 miles east of
Valognes, near Cherbourg, France. Meteor ended
23 miles in height, over Calais, France. Length of
path 175 miles. Radiant point, 280°, 12°." l

It was decided some years ago " in the
American Supreme Court that a meteorite, though
a stone fallen from heaven, belongs to the owner
of the freehold interest in the land 011 which it
falls, and not to the tenant." 2

With reference to the fall of meteoric matter
on the earth, Mr. Proctor says, " It is calculated
by Dr. Kleiber of St. Petersburg!! that 4250 Ibs. of
meteoric dust fall on the earth every hour — that
is, 59 tons a day, and more than 11,435 tons a
year. I believe this to be considerably short of
the truth. It sounds like a large annual growth,
and the downfall of such an enormous mass of
meteoric matter seems suggestive of some degree
of danger. But in reality, Dr. Kleiber' s estimate
gives only about 25 millions of pounds annually,
which is less than 2 ounces annually to each
square mile of the earth's surface," 3 a quantity
which is, of course, quite insignificant.

1 The Observatory, February, 1900, pp. 106-7.
• Knowledge, March, 1893, p. 51.
3 llnil, July 3, 1835, p. 11.

124 ASTRONOMICAL CURIOSITIES

According to Humboldt, Chladiii states that a
Franciscan monk was killed by the fall of an
aerolite at Milan in the year 1660.1 Humboldt
also mentions the death by meteoric stones of a
monk at Crema on September 4, 1511, and two
Swedish sailors on board ship in 1674.2

It is a curious fact that, according to Olbers,
" no fossil meteoric stones " have ever been dis-
covered.3 Considering the number which are
supposed to have fallen to the earth in the course
of ages, this fact seems a remarkable one.

On May 10, 1879, a shower of meteorites fell at
Eitherville, Iowa (U.S.A.). Some of the fragments
found weighed 437, 170, 92^, 28, 10J, 4 and 2 Ibs.
in weight. In the following year (1880) when the
prairie grass had been consumed by a fire, about
" 5000 pieces were found from the size of a pin to
a pound in weight." 4

According to Prof. Silvestria of Catania, a
shower of meteoric dust mixed with rain fell on
the night of March 29, 1880. The dust contained
a large proportion of iron in the metallic state.
In size the particles varied from a tenth to a
hundredth of a millimetre.5

It is sometimes stated that the average mass of
a " shooting star " is only a few grains. But from

1 Cosmos, vol. i. p. 108 (Otte's translation).

2 Ibid., vol. i. p. 124.

3 Ibid., vol. i. p. 119, footnote.

4 Copernicus, vol. i. p. 72.

5 Ibid.

METEORS 125

comparisons with an electric arc light, Prof. W.
II. Pickering concludes that a meteor as bright as
a third magnitude star, composed of iron or stone,
would probably have a diameter of 6 or 7 inches.
An average bright fireball would perhaps measure
5 or 6 feet in diameter.1

In the Book of Joshua we are told "that the
LORD cast down great stones from heaven upon
them unto Azekah, and they died " (Joshua x. 11).
In the latter portion of the verse " hailstones " are
mentioned, but as the original Hebrew word
means stones in general (not hailstones), it seems
very probable that the stones referred to were
aerolites.2

The stone mentioned in the Acts of the Apostles,
from which was found " the image which fell
down from Jupiter " (Acts xix. 35), was evidently
a meteoric stone.2

The famous stone in the Caaba at Mecca, is
probably a stone of meteoric origin.3

" Stones from Heaven ! Can you wonder,

You who scrutinize the Earth,
At the love and veneration

They received before the birth
Of our scientific methods ?

" Stones from Heaven ! we can handle

Fragments fallen from realms of Space ;

1 Astrophysical Journal, June, 1909, pp. 378-9.

2 Knowledge, July, 1909, p. 264.

126 ASTRONOMICAL CURIOSITIES

Oh ! the marvel and the mystery,

Could we understand their place
In the scheme of things created !

Ill

" Stones from Heaven ! With a mighty

Comet whirling formed they part ?
Fell they from their lofty station

Like a brilliant fiery dart,
Hurl'd from starry fields of Night?" »

1 Quoted by Miss Irene E. T. Warner in Knowledge, July, 19CW,
p. 261.

CHAPTER XIII

The Zodiacal Light and Gegenschein

ACCORDING to Gruson and Brugsch, the
Zodiacal Light was known in ancient
times, and was even worshipped by the
Egyptians. Strabo does not mention it; but
Diodorus Siculus seems to refer to it (B.C. 373),
and he probably obtained his information from
some Greek writers before his time, possibly
from Zenophon, who lived in the sixth century
B.C.1 Coming to the Christian era, it was noticed
by Nicephorus, about 410 B.C. In the Koran, it is
called the " false Aurora " ; and it is supposed to be
referred to in the " Rubaiyat " of Omar Khayyam,
the Persian astronomical poet, in the second stanza
of that poem (Edward Fitzgerald's translation) —

" Dreaming when Dawn's Left Hand was in the Sky,2
I heard a voice within the Tavern cry,
Awake, my Little ones, and fill the Cup,
Before Life's Liquor in its Cup be dry."

It was observed by Cassini in 1668,* and by

1 The Observatory, November, 1900.

2 Or, " Before the phantom of false morning died " (4th edition) ;
The Observatory, September, 1905, p. 356.

3 The Observatory, July, 1896, p. 274.

128 ASTRONOMICAL CURIOSITIES

Hooke in 1705. A short description of its appear-
ance will be found in; Childrey's Britannia
Baconica (1661), p. 183.

The finest displays of this curious light seem to
occur between the middle of January and the
middle of February. In February, 1856, Secchi
found it brighter than he had ever seen it before.
It was yellowish towards the axis of the cone,
and it seemed to be brighter than the Milky Way
in Cygnus. He described it as " un graiide
spectacle." In the middle of February, 1866, Mr.
Lassell, during his last residence in Malta, saw
a remarkable display of the Zodiacal Light. He
found it at least twice as bright as the brightest
part of the Milky Way, and much brighter than
he had previously seen it. He found that the
character of its light differed considerably from
that of the Milky Way. It was of a much redder
hue than the Galaxy. In 1874 very remarkable
displays were seen in the neighbourhood of
London in January and February of that year ;
and in 1875 on January 24, 25, and 30. On
January 24 it was noticed that the "light" was
distinctly reddish and much excelled in brightness
any portion of the Milky Way.

Humboldt, who observed it from Andes (at a
height of 13,000 to 15,000 feet), from Venezuela
and from Cumana, tells us that he has seen the
Zodiacal Light equal in brightness to the Milky
Way in Sagittarius.

THE ZODIACAL LIGHT 129

As probably many people have never seen the
" light," a caution may be given to those who
care to look for it. It is defined by the Rev.
George Jones, Chaplain to the " United States'
Japan Expedition" (1853-55), as "a brightness
that appears in the western sky after sunset, and
in the east before sunrise ; following nearly or
quite the line of the ecliptic in the heavens,
and stretching upwards to various elevations
according to the season of the year." From the
description some might suppose that the light is
visible immediately after sunset. But this is not
so ; it never appears until twilight is over and
" the night has fully set in."

The " light " is usually seen after sunset or
before sunrise. But attempts have recently
been made by Prof. Simon Newcomb to observe
it north of the sun. To avoid the effects of
twilight the sun must be only slightly more
than 18° below the horizon (that is, a little
before or after the longest day). This condition
limits the place of observation to latitudes not
much south of 46°; and to reduce atmospheric
absorption the observing station should be as
high as possible above the level of the sea. Prof.
Newcomb, observing from the Brienzer Rothorn in
Switzerland (latitude 46° 47' N., longitude 8° 3' E.),
succeeded in tracing the "light" to a distance of
35° north of the sun. It would seem, therefore,
that the Zodiacal Light envelops the sun on all

130 ASTRONOMICAL CURIOSITIES

sides, but has a greater extension in the direction
of the ecliptic.1 From observations at the Lick
Observatory, Mr. E. A. Fath found an extension
of 46° north of the sun.2

From observations of the "light" made by
Prof. Barnard at the Yerkes Observatory during
the summer of 1906, he finds that it extends to at
least 65° north of the sun, a considerably higher
value than that found by Prof. Newcomb.3 The
difference may perhaps be explained by actual
variation of the meteoric matter producing the
light. Prof. J. H. Poynting thinks that possibly
the Zodiacal Light is due to the "dust of long
dead comets." 4

From careful observations of the "light," Mr.
Gavin J. Burns finds that its luminosity is " some
40 or 50 per cent, brighter than the background
of the sky. Prof. Newcomb has made a precisely
similar remark about the luminosity of the Milky
Way, viz. that it is surprisingly small." This
agrees with my own observations during many
years. It is only on the finest and clearest nights
that the Milky Way forms a conspicuous object
in the night sky. And this only in the country.
The lights of a city almost entirely obliterate
it. Mr. Burns finds that the Zodiacal Light

1 Journal, B.A.A., January 24, 1906.

- Ast. Soc. of the Pacific, December, 1908, p. 280.

3 Nature, November 1, 1906.

4 Ibid., November 22, 1906, p. 93.

THE ZODIACAL LIGHT 131

appears " to be of a yellowish tint ; or if we call
it white, then the Milky Way is comparatively of
a bluish tint." During my residence in the Punjab
the Zodiacal Light seemed to me constantly
visible in the evening sky in the spring months.
In the west of Ireland I have seen it nearly as
bright as the brightest portions of the Milky Way
visible in this country (February 20, 1890). The
" meteoric theory " of the " light " seems to be
the one now generally accepted by astronomers,
and in this opinion I fully concur.

From observations made in Jamaica in the years
1899 and 1901, Mr. Maxwell Hall arrived at the
conclusion that " the Zodiacal Light is caused by
reflection of sunlight from masses of meteoric
matter still contained in the invariable plane,
which may be considered the original plane of the
solar system." l According to Humboldt, Cassini
believed that the Zodiacal Light "consisted of
innumerably small planetary bodies revolving
round the sun." 2

THE GEGENSCHEIN, or COUNTER-GLOW. — This is
a faint patch of light seen opposite the sun's
place in the sky, that is on the meridian at mid-
night. It is usually elliptical in shape, with its
longer axis lying nearly in the plane of the
ecliptic. It seems to have been first detected by
Brorsen (the discoverer of the short-period comet

1 Nature, August 30, 1906.

- Cosmos, vol. i. p. 131, footnote.

132 ASTRONOMICAL CURIOSITIES

of 1846) about the middle of the nineteenth
century. But it is not easy to see, for the famous
Heis of Munster, who had very keen eyesight, did
not succeed in seeing it for several years after
Brorsen's announcement.1 It was afterwards
independently discovered by Backhouse, and
Barnard.

Prof. Barnard's earlier observations seemed to
show that the Gegenschein does not lie exactly
opposite to the sun, but very nearly so. He
found its longitude is within one degree of 180°,
and its latitude about 1°'3 north of the ecliptic.2
But from subsequent observations he came to the
conclusion that the differences in longitude and
apparent latitude are due to atmospheric absorp-
tion, and that the object really lies in the ecliptic
and exactly opposite to the sun.3

Barnard finds that the Gegenschein is not so
faint as is generally supposed. He says " it is
best seen by averted vision, the face being turned
60° or 70° to the right or left, and the eyes alone
turned towards it." It is invisible in June and
December, while in September it is round, with a
diameter of 20°, and very distinct. No satis-
factory theory has yet been advanced to account
for this curious phenomenon. Prof. Arthur
Searle of Harvard attributes it to a number of

1 Nature, December 16, 1875.

2 Ibid., July 23, 1891.

3 Bulletin, Ast. Soc. de France, April, 1903.

THE ZODIACAL LIGHT 133

asteroids too small to be seen individually.
When in " opposition " to the sun these would
be fully illuminated and nearest to the earth.
Its distance from the earth probably exceeds
that of the moon. Dr. Johnson Stoney thinks
that the Gegenschein may possibly be due to a
"tail" of hydrogen and helium gases repelled
from the earth by solar action ; this " tail " being
visible to us by reflected sunlight.

It was observed under favourable circumstances
in January and February, 1903, by the French
astronomer, M. F. Quenisset. He found that it
was better seen when the atmosphere was less
clear, contrary to his experience of the Zodiacal
Light. Prof. Barnard's experience confirms this.
M. Quenisset notes that — as in the case of the
Zodiacal Light — the southern border of the
Gegenschein is sharper than the northern. He
found that its brightness is less than that of the
Milky Way between Betelgeuse and y Geminorum ;
and thinks that it is merely a strengthening of
the Zodiacal Light.1

A meteoritic theory of the Gegenschein has
been advanced by Prof. F. R. Moulton, which
explains it by light reflected from a swarm of
meteorites revolving round the sun at a distance
of 930,240 miles outside the earth's orbit.

Both the Zodiacal Light and Gegenschein were
observed by Herr Leo Brenner on the evening of
1 Bulletin, Ast. Soc. de France, April, 1903.

134 ASTRONOMICAL CURIOSITIES

March 4, 1896. He found the Zodiacal Light on
this evening to be "perhaps eight times brighter
than the Milky Way in Perseus." The " Gegen-
schein distinctly visible as a round, bright, cloud-
like nebula below Leo (Virgo), and about twice
the brightness of the Milky Way in Monoceros
between Canis Major and Canis Minor." *

Humboldt thought that the fluctuations in the
brilliancy of the Zodiacal Light were probably
due to a real variation in the intensity of the
phenomenon rather than to the elevated position
of the observer.2 He says that he was " astonished
in the tropical climates of South America, to
observe the variable intensity of the light."

1 The Observatory, May, 1896. The italics are Brenner's.

2 Cosmos, vol. iv. p. 563.

CHAPTER XIV

The Stars

PLINY says that Hipparchus " ventured to
count the stars, a work arduous even for
the Deity." But this was quite a mis-
taken idea. Those visible to the naked eye are
comparatively few in number, and the enumera-
tion of those visible in an opera-glass — which of
course far exceed those which can be seen by un-
aided vision — is a matter of no great difficulty.
Those visible in a small telescope of 2| inches
aperture have all been observed and catalogued ;
and even those shown on photographs taken with
large telescopes can be easily counted. The pre-
sent writer has made an attempt in this direction,
and taking an average of a large number of counts
in various parts of the sky, as shown on stellar
photographs, he finds a total of about 64 millions
for the whole sky in both hemispheres.1 Prob-
ably the total number will not exceed 100
millions. But this is a comparatively small

1 For details of this enumeration, see Astronomical Essays,
p. 222.

136 ASTRONOMICAL CURIOSITIES

number, even when compared with the human
population of our little globe.

With reference to the charts made by photo-
graphy in the International scheme commenced
some years ago, it has now been estimated that
the charts will probably contain a total of about
9,854,000 stars down to about the 14th magnitude
(13-7). The "catalogue plates" (taken with a
shorter exposure) will, it is expected, include about
2,676,500 stars down to 11J magnitude. These
numbers may, however, be somewhat increased
when the work has been completed.1 If this
estimate proves to be correct, the number of stars
visible down to the 14th magnitude will be con-
siderably less than former estimates have made it.

Prof. E. C. Pickering estimates that the total
number of stars visible on photographs down to
the 16th magnitude (about the faintest visible
in the great Lick telescope) will be about 50
millions.2 In the present writer's enumeration,
above referred to, many stars fainter than the
16th magnitude were included.

Admiral Smyth says, with reference to Sir
William Herschel — perhaps the greatest observer
that ever lived — "As to Sir William himself, he
could unhesitatingly call every star down to the
6th magnitude, by its name, letter, or number." 3

1 Nature, June 11, 1908.

2 Popular Astronomy, vol. U (190G), p. 510.

3 Bedford Catalogue, p. 532.

THE STARS 137

This shows great powers of observation, and a
wonderful memory.

On a photographic plate of the Pleiades taken
with the Bruce telescope and an exposure of 6
hours, Prof. Bailey of Harvard has counted " 3972
stars within an area 2° square, having Alcyone
at its centre." l This would give a total of about
41 millions for the whole sky, if of the same
richness.

With an exposure of 16 hours, Prof. H. C.
Wilson finds on an area of less that 110' square a
total of 4621 stars. He thinks, " That all of these
stars belong to the Pleiades group is not at all
probable. The great majority of them probably
lie at immense distances beyond the group, and
simply appear in it by projection." l He adds,
" It has been found, however, by very careful
measurements made during the last 75 years
at the Konigsbergh and Yale Observatories,
that of the sixty-nine brighter stars, including
those down to the 9th magnitude, only eight
show any certain movement with reference to
Alcyone. Since Alcyone has a proper motion or
drift of 6" per century, this means that all the
brightest stars except the eight mentioned are
drifting with Alycone and so form a true cluster,
at approximately the same distance from the
earth. Six of the eight stars which show relative
drift are moving in the opposite direction to the
1 Popular Astronomy, Yol. 15 (1907), p. 194.

138 ASTRONOMICAL CURIOSITIES

movement of Alycone, and at nearly the same
rate, so that their motion is only apparent. They
are really stationary, while Alycone and the
rest of the cluster are moving past them." l
This tends to show that the faint stars are
really behind the cluster, and are unconnected
with it.

It is a popular idea with some people that
the Pole Star is the nearest of all the stars to
the celestial pole. But photographs show that
there are many faint stars nearer to the pole
than the Pole Star. The Pole Star is at present
at a distance of 1° 13' from the real pole of the
heavens, but it is slowly approaching it. The
minimum distance will be reached in the year
2104. Prom photographs taken by M. Flammarion
at the Juvisy Observatory, he finds that there are
at least 128 stars nearer to the pole than the
Pole Star ! The nearest star to the pole was, in
the year 1902, a small star of about 12J magni-
tude, which was distant about 4 minutes of arc
from the pole.2 The estimated magnitude shows
that the Pole Star is nearly 10,000 times brighter
than this faint star !

It has been found that Sirius is bright enough
to cast a shadow under favourable conditions.
On March 22, 1903, the distinguished French
astronomer Touchet succeeded in photographing

1 Popular Astronomy, vol. 15 (1907), p. 195.

2 Bulletin, Ast. Soc, de France, February, 1903.

THE STARS 139

the shadow of a brooch cast by this brilliant star.
The exposure was lh 5m.

Martinus Hortensius seems to have been the
first to see stars in daylight, perhaps early in
the seventeenth century. He mentions the fact
in a letter to Gassendi dated October 12, 1636,
but does not give the date of his observation.
Schickard saw Arcturus in broad daylight early
in 1632. Morin saw the same bright star half an
hour after sunset in March, 1635.

Some interesting observations were made by
Professors Payne and H. C. Wilson, in the
summer of 1904, at Midvale, Montana (U.S.A.), at
a height of 4790 feet above sea-level. At this
height they found the air very clear and trans-
parent. " Many more stars were visible at a
glance, and the familiar stars appeared more
brilliant. ... In the great bright cloud of the
Milky Way, between /? and y Cygni, one could
count easily sixteen or seventeen stars, besides
the bright ones TJ and x> while at Northfield it is
difficult to distinctly w see eight or nine with the
naked eye." Some nebulae and star fields were
photographed with good results by the aid of a
2J-inch Darlot lens and 3 hours' exposure.2

Prof. Barnard has taken some good stellar photo-
graphs with a lens of only 1J inches in diameter,

1 Here x i3 probably 17 Cygni, x being the famous variable
near it.

Popular Astronomy, vol. 13 (1904), p. 509.

HO ASTRONOMICAL CURIOSITIES

and 4 or 5 inches focus belonging to an ordinary
" magic lantern " ! He says that these " photo-
graphs with the small lens show us in the most
striking manner how the most valuable and
important information may be obtained with the
simplest means." l

With reference to the rising and setting of the
stars due to the earth's rotation on its axis, the
late Sir George B. Airy, Astronomer Royal of
England, once said to a schoolmaster, "I should
like to know how far your pupils go into the first
practical points for which reading is scarcely
necessary. Do they know that the stars rise and
set? Very few people in England know it. I
once had a correspondence with a literary man
of the highest rank on a point of Greek astronomy,
and found that he did not know it ! " 2

Admiral Smyth says, " I have been struck with
the beautiful blue tint of the smallest stars visible
in my telescope. This, however, may be attributed
to some optical peculiarity." This bluish colour
of small stars agrees with the conclusion arrived
at by Prof. Pickering in recent years, that the
majority of faint stars in the Milky Way have
spectra of the Sirian type and, like that brilliant
star, are of a bluish white colour. Sir William
Herschel saw many stars of a redder tinge than
other observers have noticed. Admiral Smyth

1 Astrophy steal Journal, December, 1895.

2 The Observatory, July, 1895, p. 290.

THE STARS 141

says, "This may be owing to the effect of his
metallic mirror or to some peculiarity of vision, or
perhaps both." l

The ancient astronomers do not mention any
coloured stars except white and red. Among the
latter they only speak of Arcturus, Aldebaran,
Pollux, Antares, and Betelgeuse as of a striking
red colour. To these Al-Sufi adds Alphard
(a Hydrse).

Sir William Herschel remarked that no decidedly
green or blue star "has ever been noticed un-
associated with a companion brighter than itself."
An exception to Herschel's rule seems to be found
in the case of the star ft Librae, which Admiral
Smyth called " pale emerald." Mr. George Kiiott
observed it on May 19, 1852, as " beautiful pale
green " (3*7 inches achromatic, power 80), and on
May 9, 1872, as "fine pale green" (5*5 inches
achromatic, power 65).

The motion of stars in the line of sight, as shown
by the spectroscope — should theoretically alter
their brightness in the course of time ; those ap-
proaching the earth becoming gradually brighter,
while those receding should become fainter.
But the distance of the stars is so enormous that
even with very high velocities the change would
not become perceptible for ages. Prof. Oudemans
found that to change the brightness of a star by
only one-tenth of a magnitude — a quantity barely
? Celestial Cycle, p. 302.

142 ASTRONOMICAL CURIOSITIES

perceptible to the eye — a number of years would
be necessary, which is represented by the formula

5916 years
parallax X motion

for a star approaching the earth, and for a reced-
ing star

6195 years
p X m

This is in geographical miles, 1 geographical mile
being equal to 4*61 English miles.

Reducing the above to English miles, and taking
an average for both approaching and receding
stars, we have

27,660 years
p X m

where p = parallax in seconds '\ of arc, and
m = radial velocity in English miles per second.

Prof. Oudemans found that the only star which
could have changed in brightness by one-tenth of
a magnitude since the time of Hipparchus is
Aldebaran. This is taking its parallax as 0"*52.
But assuming the more reliable parallax 0"*12
found by Dr. Elkin, this period is 4J times longer.
For Procyon, the period would be 5500 years.1
The above calculation shows how absurd it is to
suppose that any star could have gained or lost in
brightness by motion in the line of sight during
historical times. The " secular variation " of stars
1 Nature, December 13, 1894.

THE STARS 143

is quite another thing. This is due to physical
changes in the stars themselves.

The famous astronomer Halley, the second
Astronomer Royal at Greenwich, says (Phil.
Trans., 1796), " Supposing the number of 1st
magnitude stars to be 13, at twice the distance
from the sun there may be placed four times as
many, or 52 ; which with the same allowance
would nearly represent the star we find to be of
the 2nd magnitude. So 9 x 13, or 117, for those at
three times the distance; and at ten times the
distance 100 X 13, or 1300 stars ; of which distance
may probably diminish the light of any of the
stars of the 1st magnitude to that of the 6th,
it being but the hundredth part of what, at their
present distance, they appear with." This agrees
with the now generally accepted " light ratio " of
2'512 for each magnitude, which makes a first
magnitude star 100 times the light of a 6th
magnitude.

On the 4th of March, 1796,1 the famous French
astronomer Lalande observed on the meridian a
star of small 6th magnitude, the exact position of
which he determined. On the 15th of the same
month he again observed the star, and the places
found for 1800 refer to numbers 16292-3 of the
reduced catalogue. In the observation of March
4 he attached the curious remark, " Etoile singu-
liere " (the observation of March 15 is without
1 Hietoire Celeste, p, 211.

144 ASTRONOMICAL CURIOSITIES

note). This remark of Lalande has puzzled
observers who failed to find any peculiarity about
the star. Indeed, " the remark is a strange one for
the observer of so many thousands of stars to
attach unless there was really something singular
in the star's aspect at the time." On the evening
of April 18, 1887, the star was examined by the
present writer, and the following is the record in
his observing book, " Lalande's etoile singuliere
(16292-3) about half a magnitude less than rj Cancri.
With the binocular I see two streams of small
stars branching out from it, north preceding
like the tails of comet." This may perhaps have
something to do with Lalande's curious remark.

The star numbered 1647 in Baily's Flamsteed
Catalogue is now known to have been an obser-
vation of the planet Uranus.1

Prof. Pickering states that the fainter stars
photographed with the 8-inch telescope at Cam-
bridge (U.S.A.) are invisible to the eye in the
15-inch telescope.2

Sir Norman Lockyer finds that the lines of
sulphur are present in the spectrum of the bright
star Rigel (/? Orionis). 3

About 8J° south of the bright star Regulus
(a Leonis) is a faint nebula (H I, 4 Sextaiitis).
On or near this spot the Capuchin monk De
Rheita fancied he saw, in the year 1643, a

1 Nature, October, 1887. - Ibid., August 29, 1889.

3 Science Abstracts, February 25, 1908, pp. 82, 83.

THE STARS 145

group of stars representing the napkin of S.
Veronica — "sudarium Veronicas sive faciem Domini
maxima similitudina in astris expressum." And
he gave a picture of the napkin and star group.
But all subsequent observers have failed to find
any trace of the star group referred to by De
Rheita ! l

The Bible story of the star of the Magi is also
told in connection with the birth of the sun-gods
Osiris, Horns, Mithra, Serapis, etc.2 The present
writer has also heard it suggested that the
phenomenon may have been an apparition of
Halley's comet! But as this famous comet is
known to have appeared in the year B.C. 11, and as
the date of the Nativity was probably not earlier
than B.C. 5, the hypothesis seems for this (and
other reasons) to be inadmissible. It has also
been suggested that the phenomenon might have
been an appearance of Tycho Brahe's temporary
star of 1572, known as the " Pilgrim star " ; but
there seems to be no real foundation for such an
hypothesis. There is no reason to think that
" temporary " or new stars ever appear a second
time.

Admiral Smyth has well said, " It checks one's
pride to recollect that if our sun with the whole
system of planets, asteroids, and moons, and
comets were to be removed from the spectator

1 Bedford Catalogue, pp. 227-8,

2 Knowledge, February 1, 1888.

146 ASTRONOMICAL CURIOSITIES

to the distance of the nearest fixed star, not one
of them would be visible, except the sun, which
would then appear but as a star of perhaps the
2nd magnitude. Nay, more, were the whole
system of which our globe forms an insignificant
member, with its central luminary, suddenly
annihilated, no effect would be produced on those
unconnected and remote bodies; and the only
annunciation of such a catastrophe in the Sidereal
"Times" would be that a small star once seen
in a distant quarter of the sky had ceased to
shine." l

Prof. George C. Comstock finds that the average
parallax of 67 selected stars ranging in brightness
between the 9th and the 12th magnitude, is of
the value of 0"*0051.2 This gives a distance repre-
senting a journey for light of about 639 years !

Mr. Henry Norris Russell thinks that nearly
all the bright stars in the constellation of Orion
are practically at the same distance from the
earth. His reasons for this opinion are : (1) the
stars are similar in their spectra and proper
motions, (2) their proper motions are small, which
suggests a small parallax, and therefore a great
distance from the earth. Mr. Russell thinks that
the average parallax of these stars may perhaps
be 0"-005, which gives a distance of about 650
" light years." 3

1 Celestial Cycle, p. 280. * Popular Astronomy, February, 1904.
3 Ibid., vol. 15 (1907), p. 444.

THE STARS 147

According to Sir Norman Lockyer's classifica-
tion of the stars, the order of increasing tempera-
ture is represented by the following, beginning
with those in the earliest stage of stellar evo-
lution : — Nebulae, Antares, Aldebaran, Polaris,
a Cygni, Rigel, c Tauri, ft Crucis. Then we have
the hottest stars represented by e Puppis, y Argus,
and Alnitam (c Orionis). Decreasing temperature
is represented by (in order), Achernar, Algol,
Markab, Sirius, Procyon, Arcturus, 19 Piscium,
and the "Dark Stars."1 But other astronomers
do not agree with this classification. Antares
and Aldebaran are by some authorities considered
to be cooling suns.

According to Ritter's views of the Constitution
of the Celestial Bodies, if we "divide the stars
into three classes according to age corresponding
to these three stages of development, we shall
assign to the first class, A, those stars still in
the nebular phase of development ; to the second
class, B, those in the transient stage of greatest
brilliancy ; and to the class C, those stars which
have already entered into the long period of slow
extinction. It should be noted in this classifica-
tion that we refer to relative and not absolute
age, since a star of slight mass passes through
the successive phases of its development more
rapidly than the star of greater mass." 2 Ritter

1 Journal, B.A.A., June, 1899.

• Astrophysical Journal, vol. 8 (1898), p. 314.

148 ASTRONOMICAL CURIOSITIES

conies to the conclusion that "the duration of
the period in which the sun as a star had a
greater brightness than at present was very
short in comparison with the period in which
it had and will continue to have a brightness
differing only slightly from its present value." l

In a valuable and interesting paper on "The
Evolution of Solar Stars,"2 Prof. Schuster says
that " measurements by E. P. Nichols on the
heat of Vega and Arcturus indicated a lower
temperature for Arcturus, and confirms the
conclusion arrived at on other grounds, that the
hydrogen stars have a higher temperature than
the solar stars." "An inspection of the ultra-
violet region of the spectrum gives the same
result. These different lines of argument, all
leading to the same result, justify us in saying
that the surface temperature of the hydrogen
stars is higher than that of the solar stars. An
extension of the same reasoning leads to the
belief that the helium stars have a temperature
which is higher still." Hence we have Schuster,
Hale, and Sir William Huggins in agreement that
the Sirian stars are hotter than the solar stars ;
and personally I agree with these high authorities.
The late Dr. W. E. Wilson, however, held the
opinion that the sun is hotter that Sirius !

Schuster thinks that Lane's law does not apply

1 AstropJtysical Journal, vol. 8, p. 213.

2 Ibid., vol. 17, January to June, 1902.

THE STARS 149

to the temperature of the photosphere and the
absorbing layers of the sun and stars, but only
to the portions between the photosphere and the
centre, which probably act like a perfect gas. On
this view he says the interior might become
"hotter and hotter until the condensation had
reached a point at which the laws of gaseous
condensation no longer hold."

With reference to the stars having spectra of
the 3rd and 4th type (usually orange and red
in colour), Schuster says—

" The remaining types of spectra belong to lower
temperature still, as in place of metallic lines, or
in addition to them, certain bands appear which
experiments show us invariably belong to lower
temperature than the lines of the same element.

" If an evolutionary process has been going on,
which is similar for all stars, there is little doubt
that from the bright-line stars down to the solar
stars the order has been (1) helium or Orion
stars, (2) hydrogen or Sirian stars, (3) calcium
or Procyon stars, (4) solar or Capellan stars."

My investigations on "The Secular Variation
of Starlight" (Studies in Astronomy, chap. 17,
and Astronomical Essays, chap. 12) based on a
comparison of Al-Sufi's star magnitudes (tenth
century) with modern estimates and measures,
tend strongly to confirm the above views.

With regard to the 3rd-type stars, such as
Betelgeuse and Mira Ceti, Schuster says, " It has
been already mentioned that observers differ as

150 ASTRONOMICAL CURIOSITIES

to whether their position is anterior to the
hydrogen or posterior to the solar stars, and
there are valid arguments on both sides."

Scheiner, however, shows, from the behaviour
of the lines of magnesium, that stars of type I.
(Sirian) are the hottest, and type III. the coolest,
and he says, we have " for the first time a direct
proof of the correctness of the physical inter-
pretation of Vogel's spectral classes, according
to which class II. is developed by cooling from I.,
and III. by a further process of cooling from II." l
Prof. Hale says that " the resemblance between
the spectra of sun-spots and of 3rd-type stars
is so close as to indicate that the same cause is
controlling the relative intensities of many lines
in both instances. This cause, as the laboratory
work indicates, is to be regarded as reduced
temperature." 2

According to Prof. Schuster, "a spectrum of
bright lines may be given by a mass of luminous
gas, even if the gas is of great thickness. There
is, therefore, no difficulty in explaining the exist-
ence of stars giving bright lines." He thinks
that the difference between "bright line" stars
and those showing dark lines depends upon the
rate of increase of the temperature from the
surface towards the centre. If this rate is slow,
bright lines will be seen. If the rate of increase

1 Astronomy and Astrophysics, 1894, pp. 5G9-70.

2 The Study of Stellar Evolution (1908), p. 171.

THE STARS 151

is rapid, the dark-line spectrum shown by the
majority of the stars will appear. This rate,
he thinks, is regulated by the gravitational force.
So that in the early stages of condensation bright
lines are more likely to occur. " If the light is
not fully absorbed," both bright and dark lines
of the same element may be visible in the same
star. Schuster considers it quite possible that
if we could remove the outer layers of the Sun's
atmosphere, we should obtain a spectrum of
bright lines.1

M. Stratonoff finds that stars having spectra
of the Orion and Sirian types — supposed to repre-
sent an early stage in stellar evolution — tend to
congregate in or near the Milky Way. Star
clusters in general show a similar tendency, " but
to this law the globular clusters form an excep-
tion." 2 We may add that the spiral nebulae —
which seem to be scattered indifferently over all
parts of the sky — also seem to form an exception ;
for the spectra of these wonderful objects seem
to show that they are really star clusters, in
which the components are probably relatively
small; that is, small in comparison with our
sun.

If we accept the hypothesis that suns and
systems were evolved from nebulae, and if we
consider the comparatively small number of

1 Astrophysical Journal, January, 1905.

2 Journal, B.A.A., June, 1901.

152 ASTRONOMICAL CURIOSITIES

nebulae hitherto discovered in the largest tele-
scopes— about half a million ; and if we further
consider the very small number of red stars, or
those having spectra of the third and fourth
types — usually considered to be dying-out suns —
we seem led to the conclusion that our sidereal
system is now at about the zenith of its life-
history; comparatively few [nebulae being left
to consolidate into stars, and comparatively few
stars having gone far on the road to the final
extinction of their light.

Prof. Boss of Albany (U.S.A.) finds that about
forty stars of magnitudes from 3J to 7 in the
constellation Taurus are apparently drifting
together towards one point. These stars are
included between about R.A. 3h 47m to 5h 4m, and
Declination -f- 5° to 4- 23° (that is, in the region sur-
rounding the Hyades). These motions apparently
converge to a point near R.A. 6h, Declination -f- 7°
(near Betelgeuse). Prof. Boss has computed the
velocity of the stars in this group to be 45*6
kilometres (about 28 miles) a second towards
the " vanishing point," and he estimated the
average parallax of the group to be 0"*025 — about
130 years' journey for light. Although the motions
are apparently converging to a point, it does not
follow that the stars in question will, in the course
of ages, meet at the " vanishing point. " On the
contrary, the observed motions show that the
stars are moving in parallel lines through space.

THE STARS 153

About 15 kilometres of the observed speed is due
to the sun's motion through space in the opposite
direction. Prof. Campbell finds from spectro-
scopic measures that of these forty stars, nine are
receding from the earth with velocities varying
from 12 to 60 kilometres a second, and twenty-
three others with less velocities than 38 kilo-
metres.1 It will be obvious that, as there is a
" vanishing point," the motion in the line of
sight must be one of recession from the earth.

It has been found that on an average the
parallax of a star is about one-seventh of its
" proper motion." 2

Adopting Prof. Newcomb's parallax of 0"*14 for
the famous star 1830 Groombridge, the velocity
perpendicular to the line of sight is about 150
miles a second. The velocity in the line of sight
— as shown by the spectroscope — is 59 miles a
second approaching the earth. Compounding
these two velocities we find a velocity through
space of about 161 miles a second ! '

An eminent American writer puts into the
mouth of one of his characters, a young
astronomer, the following : —

" I read the page
Where every letter is a glittering sun."

From an examination of the heat radiated by

1 A*t. Soc. of the Pacific, December, 1908.

2 TJie Observatory, November, 1902, p. 391.

154 ASTRONOMICAL CURIOSITIES

some bright stars, made by Dr. E. F. Nicholls in
America with a very sensitive radiometer of his
own construction, he finds that "we do not
receive from Arcturus more heat than we should
from a candle at a distance of 5 or 6 miles."

With reference to the progressive motion of
light, and the different times taken by light
to reach the earth from different stars, Humboldt
says, " The aspect of the starry heavens presents
to us objects of unequal date. Much has long
ceased to exist before the knowledge of its pre-
sence reaches us ; much has been otherwise
arranged." 1

The photographic method of charting the stars,
although a great improvement on the old system,
seems to have its disadvantages. One of these is
that the star images are liable to disappear from
the plates in the course of time. The reduction
of stellar photograph plates should, therefore, be
carried out as soon as possible after they are
taken. The late Dr. Roberts found that on a
plate originally containing 364 stars, no less than
180 had completely disappeared in 9£ years !

It has been assumed by some writers on
astronomy that the faint stars visible on photo-
graphs of the Pleiades are at practically the same
distance from the earth as the brighter stars of the
cluster, and that consequently there must be an
enormous difference in actual size between the
1 Cosmos, vol. iv. p. 567 (Otte's translation).

THE STARS 155

brighter and fainter stars. But there is really no
warrant for any such assumption. Photographs
of the vicinity show that the sky all round the
Pleiades is equally rich in faint stars. It seems,
therefore, more reasonable to suppose that most
of the faint stars visible in the Pleiades are really
far behind the cluster in space. For if all the
faint stars visible on photographs belonged to the
cluster, then if we imagine the cluster removed,
a " hole " would be left in the sky, which is of
course utterly improbable, and indeed absurd.
An examination of the proper motions tends to
confirm this view of the matter, and indicates that
the Pleiades cluster is a comparatively small one
and simply projected on a background of fainter
stars.

It has long been suspected that the famous
star 61 Cygni, which is a double star, forms a
binary system — that is, that the two stars com-
posing it revolve round their common centre of
gravity and move together through space. But
measures of parallax made by Herman S. Davis
and Wilsing seem to show a difference of parallax
between the two components of about 0*08 of a
second of arc. This difference of parallax implies
a distance of about 2f " light years " between the
two stars, and "if this is correct, the stars are
too remote to form a binary system. The proper
motions of 5"*21 and 5"*15 seem to show that they
are moving in nearly parallel directions ; but are

156 ASTRONOMICAL CURIOSITIES

probably slowly separating. Mr. Lewis, however,
thinks that a physical connection probably exists.1
Dante speaks of the four bright stars of the
Southern Cross as emblematical of the four
cardinal virtues, Justice, Temperance, Fortitude,
and Prudence ; and he seems to refer to the stars
Canopus, Achernar, and Foomalhaut under the
symbols of Faith, Hope, and Charity. The so-
called " False Cross " is said to be formed by the
stars K, 8, c, and t of the constellation Argo
Navis. But it seems to me that a better (although
larger) cross is formed by the stars a Centauri and
a, /?, and y of Triangulum Australis.

Mr. Monck has pointed out that the names of
the brightest stars seem to be arranged alpha-
betically in order of colour, beginning with red
and ending with blue. Thus we have Aldebaraii,
Arcturus, Betelgeuse, Capella, Procyon, Regulus,
Rigel, Sirius, Spica and Vega. But as the origin
of these names is different, this must be merely a
curious coincidence.2 And, to my eye at least,
Betelgeuse is redder than Arcturus.

The poet Longfellow speaks of the —

" Stars, the thoughts of God in the heavens," 3
and Drayton says —

" The stars to me an everlasting book
In that eternal register, the sky." *

1 Journal, B.A.A., February, 1898.

2 The Observatory, April, 1887.

3 Evangeline, Part the Second, III.

4 Legend of Rolwt, Duke of Normandy.

THE STARS 157

Observing at a height of 12,540 feet on the
Andes, the late Dr. Copeland saw Sirius with the
naked eye less than 10 minutes before sunset.1 He
also saw Jupiter 3m 4.7s before sunset; and the
following bright stars — Canopus, Om 523 before
sunset ; Rigel (/3 Orionis) 16m 32s after sunset ;
and Procyon llm 28s after sunset. From a height
of 12,050 feet at La Paz, Bolivia, he saw with the
naked eye in February, 1883, ten stars in the
Pleiades in full moonlight, and seventeen stars
in the Hyades. He also saw o- Tauri double.2

Humboldt says, "In whatever point the vault
of heaven has been pierced by powerful and
far-penetrating telescopic instruments, stars or
luminous nebulae are everywhere discoverable,
the former in some cases not exceeding the 20th
or 24th degree of telescopic magnitude." 3 But
this is a mistake. No star of even the 20th
magnitude has ever been seen by any telescope.
Even on the best photographic plates it is doubt-
ful that any stars much below the 18th magnitude
are visible. To show a star of the 20th magnitude
— if such stars exist — would require a telescope
of 144 inches or 12 feet in aperture. To show a
star of the 24th magnitude — if such there be — an
aperture of 33 feet would be necessary 1 4

1 Copernicus, vol. iii. p. 231.

2 Ibid., p. 61.

3 Cosmos, vol. i. p. 142.

4 These apertures are computed from the formula, minimum
visible = 9 + 5 log. aperture.

158 ASTRONOMICAL CURIOSITIES

It is a popular idea that stars may be seen in
the daytime from the bottom of a deep pit or
high chimney. But this has often been denied.
Humboldt says, "While practically engaged in
mining operations, I was in the habit, during
many years, of passing a great portion of the day
in mines where I could see the sky through deep
shafts, yet I never was able to observe a star." 1

Stars may, however, be seen in the daytime
with even small telescopes. It is said that a
telescope of 1 inch aperture will show stars of
the 2nd magnitude; 2 inches, stars of the 3rd
magnitude ; and 4 inches, stars of the 4th magni-
tude. But I cannot confirm this from personal
observation. It may be so, but I have not tried
the experiment.

Sir George Darwin says —

" Human life is too short to permit us to watch
the leisurely procedure of cosmical evolution, but
the celestial museum contains so many exhibits
that it may become possible, by the aid of
theory, to piece together, bit by bit, the processes
through which stars pass in the course of their
evolutions." 2

The so-called " telluric lines " seen in the solar
spectrum, are due to water vapour in the earth's
atmosphere. As the light of the stars also
passes through the atmosphere, it is evident that
these lines should also be visible in the spectra

1 Coamos, vol. iii. p. 73.

• Darwin and Modern Science, p. 5G3.

THE STARS 159

of the stars. This is found to be the case by
Prof. Campbell, Director of the Lick Observatory,
who has observed all the principal bands in the
spectrum of every star he has examined.1

The largest " proper motion " now known is
that of a star of the 8 J magnitude in the southern
hemisphere, known as Cordoba Zone V. No. 243.
Its proper motion is 8*07 seconds of arc per annum,
thus exceeding that of the famous "runaway
star," 1830 Groombridge, which has a proper
motion of 7'05 seconds per annum. This greater
motion is, however, only apparent. Measures of
parallax show that the southern "runaway"
is much nearer to us than its northern rival, its
parallax being 0"*32, while that of Groombridge
1830 is only 0"'14. With these data the actual
velocity across the line of sight can be easily
computed. That of the southern star comes out
80 miles a second, while that of Groombridge 1830
is 148 miles a second. The actual velocity of
Arcturus is probably still greater.

The poet Barton has well said —

" The stars ! the stars ! go forth at night,

Lift up thine eyea on high,
And view the countless orbs of light,

Which gem the midngiht sky.
Go forth in silence and alone,

This glorious sight to scan,
And bid the humbled spirit own

The littleness of man."

1 Journal, B.A.A., October, 1895.

CHAPTER XV

Double and Binary Stars

PROF. R. G. AITKEN, the eminent American
observer of double stars, finds that of all
the stars down to the 9th magnitude
— about the faintest visible in a powerful bino-
cular field-glass — 1 in 18, or 1 in 20, on the
average, are double, with the component stars less
than 5 seconds of arc apart. This proportion of
double stars is not, however, the same for all
parts of the sky; while in some regions double
stars are very scarce, in other places the propor-
tion rises to 1 in 8.

For the well-known binary star Castor (a Gemi-
norum), several orbits have been computed with
periods ranging from 232 years (Madler) to 1001
years (Doberck). But Burnham finds that " the
orbit is absolutely indeterminate at this time,
and likely to remain so for another century
or longer." l Both components are spectroscopic
binaries, and the system is a most interesting
one.

The well-known companion of Sirius became
1 Burnham's General Catalogue of Double Stars, p. 494.

DOUBLE AND BINARY STARS 161

invisible in all telescopes in the year 1890, owing
to its near approach to its brilliant primary. It
remained invisible until August 20, 1896, when
it was again seen by Dr. See at the Lowell Obser-
vatory.1 Since then its distance has been increas-
ing, and it has been regularly measured. The
maximum distance will be attained about the
year 1922.

The star ft Cephei has recently been discovered
to be a spectroscopic binary with the wonder-
fully short period of 4h 34m 11s. The orbital
velocity is about 10 J miles a second, and as this
velocity is not very great, the distance between
the components must be very small, and possibly
the two component bodies are revolving in actual
contact. The spectrum is of the " Orion type." 2

According to Slipher the spectroscopic binary
y Geminorum has the comparatively long period
(for a spectroscopic binary) of about 3| years.
This period is comparable with that of the
telescopic binary system, 8 Equulei (period about
5*7 years). The orbit is quite eccentric. I have
shown elsewhere 3 that y Geminorum has probably
increased in brightness since the time of Al-Sufi
(tenth century). Possibly its spectroscopic dupli-
city may have something to do with the variation
in its light.

1 Journal, B.A.A., November 18, 1896.

2 Ibid., B.A.A., January, 1907.

3 Studies in Astronomy, p. 185.

162 ASTRONOMICAL CURIOSITIES

With reference to the spectra of double stars,
Mr. Maunder suggests that the fact of the com-
panion of a binary star showing a Sirian spectrum
while the brighter star has a solar spectrum may
be explained by supposing that, on the theory of
fission, " the smaller body when thrown off con-
sisted of the lighter elements, the heavier
remaining in the principal star. In other words,
in these cases spectral type depends upon original
chemical constitution, and not upon the stage
of stellar development attained." l

A curious paradox with reference to binary
stars has recently come to light. For many
years it was almost taken for granted that the
brighter star of a pair had a larger mass than
the fainter component. This was a natural
conclusion, as both stars are practically at the
same distance from the earth. But it has been
recently found that in some binary stars the
fainter component has actually the larger mass !
Thus, in the binary star c Hydrae, the "magni-
tude " of the component stars are 3 and 6, indi-
cating that the brighter star is about 16 times
brighter than the fainter component. Yet cal-
culations by Lewis show that the fainter star
has 6 times the mass of the brighter, that is,
contains 6 times the quantity of matter ! In
the well-known binary 70 Ophiuchi, Prey finds
that the fainter star has about 4 times the
1 Knowledge, June, 1891.

DOUBLE AND BINARY STARS 163

mass of the brighter^! In 85 Pegasi, the brighter
star is about 40 times brighter than its companion,
Avhile Furner finds that the mass of the fainter
star is about 4 times that of the brighter !
And there are other similar cases. In fact, in
these remarkable combinations of suns the
fainter star is really the "primary," and is, so
far as mass is concerned, " the predominant
partner." This is a curious anomaly, and cannot
be well explained in the present state of our
knowledge of stellar systems. In the case of
a Centauri the masses of the components are about
equal, while the primary star is about 3 times
brighter than the other. But here the discrepancy
is satisfactorily explained by the difference in
character of the spectra, the brighter component
having a spectrum of the solar type, while the
fainter seems further advanced on the downward
road of evolution, that is, more consolidated and
having, perhaps, less intrinsic brightness of surface.
In the case of Sirius and its faint attendant,
the mass of the bright star is about twice the
mass of the satellite, while ; its light is about
40,000 times greater ! Here the satellite is either
a cooled-down sun or perhaps a gaseous nebula.
There seems to be no other explanation of this
curious paradox. The same remark applies to
Procyon, where the bright star is about 100,000
times brighter than its faint companion, although
its mass is only 5 times greater.

164 ASTRONOMICAL CURIOSITIES

The bright star Capella forms a curious anomaly
or paradox. Spectroscopic observations show
that it is a very close binary pair. It has been
seen "elongated" at the Greenwich Observatory
with the great 28-inch refractor — the work of
Sir Howard Grubb — and the spectroscopic and
visual measurements agree in indicating that its
mass is about 18 times the mass of the sun. But
its parallax (about 0"*08) shows that it is about
128 times brighter than the sun! This great
brilliancy is inconsistent with the star's computed
mass, which would indicate a much smaller
brightness. The sun placed at the distance of
Capella would, I find, shine as a star of about 5J
magnitude, while Capella is one of the brightest
stars in the sky. As the spectrum of Capella's
light closely resembles the solar spectrum, we
seem justified in assuming that the two bodies
have pretty much the same physical composi-
tion. The discrepancy between the computed
and actual brightness of the star cannot be
explained satisfactorily, and the star remains an
astronomical enigma.

Three remarkable " double-star systems have
been discovered by. Dr. See in the southern
hemisphere. The first of these is the bright star
a Phcenicis, of which the magnitude is 2'4, or only
very slightly fainter than the Pole Star. It is
attended by a faint star of the 13th magnitude
at a distance of less than 10 seconds (1897). The

DOUBLE AND BINARY STARS 165

bright star is of a deep orange or reddish colour,
and the great difference in brightness between
the component stars " renders the system both
striking and difficult." The second is /x Velorum,
a star of the 3rd magnitude, which has a com-
panion of the llth magnitude, and only 2f" from
its bright primary (1897). Dr. See describes this
pair as "one of the most extraordinary in the
heavens." The third is rj Centauri, of 2£ magitude,
with a companion of 13J magnitude at a distance
of 5"'65 (1897) ; colours yellow and purple. This
pair is " extremely difficult, requiring a powerful
telescope to see it." Dr. See thinks that these
three objects " may be regarded as amongst the
most splendid in the heavens."

The following notes are from Burnham's
recently published General Catalogue of Double
Stars. #

The Pole Star has a well-known companion of
about the 9th magnitude, which is a favourite
object for small telescopes. Burnham finds that
the bright star and its faint companion are
"relatively fixed," and are probably only an
"optical pair." Some other companions have
been suspected by amateur observers, but Burn-
ham finds that " there is nothing nearer " than the
known companion within the reach of the great
36-inch telescope of the Lick Observatory (Cat.,
p. 299).

The well-known companion to the bright star

166 ASTRONOMICAL CURIOSITIES

Rigel (/3 Orionis) has been suspected for many
years to be a close double star. Burnham con-
cludes that it is really a binary star, and its
" period may be shorter than that of any known
pair" (Cat., p. 411).

Burnham finds that the four brighter stars in
the trapezium in the great Orion nebula (in the
" sword ") are relatively fixed (Cat ., p. 426).

y Leonis. This double star was for many years
considered to be a binary, but Burnham has
shown that all the measures may be satisfactorily
represented by a straight line, and that conse-
quently the pair merely forms an " optical
double."

42 Comae Berenices. This is a binary star of
which the orbit plane passes nearly through the
earth. The period is about 25J years, and Burn-
ham says the orbit "is as accurately known as
that of any known binary."

or CoronsB Borealis. Burnham says that the
orbits hitherto computed — with periods ranging
from 195 years (Jacob) to 846 years (Doberck)
are "mere guess work," and it will require the
measures of at least another century, and perhaps
a much longer time, to give an approximate period
(Cat., p. 209). So here is some work left for
posterity to do in this field.

70 Ophiuchi. With reference to this well-
known binary star, Burnham says, " the elements
of the orbit are very accurately known." The

DOUBLE AND BINARY STARS 167

periods computed range from 86*66 years (Doo-
little) to 98-15 years (Powell). The present writer
found a period of 87'84 years, which cannot be
far from the truth. Burnham found 87'75 years
(Cat., p. 774). In this case there is not much left
for posterity to accomplish.

61 Cygni. With reference to this famous star
Burnham says, "So far the relative motion
is practically rectilinear. If the companion
is moving in a curved path, it will require
the measures of at least another half-century
to make this certain. The deviation of the
measured positions during the last 70 years from
a right line are less than the average errors of
the observations."

Burnham once saw a faint companion to Sirius
of the 16th magnitude, and measured its posi-
tion with reference to the bright star (280°'6 :
40"-25 : 1899-86). But he afterwards found that
it was "not a real object but a reflection from
Sirius " (in the eye-piece). Such false images are
called " ghosts."

With reference to the well-known double (or
rather quadruple) star e Lyrae, near Vega, and
supposed faint stars near it, Burnham says, " From
time to time various small stars in the vicinity
have been mapped, and much time wasted
in looking for and speculating about objects
which only exist in the imagination of the
observer." He believes that many of these faint

168 ASTRONOMICAL CURIOSITIES

stars, supposed to have been seen by various
observers, are merely "ghosts produced by
reflection.'*

The binary star £ Bootis, which has long been
suspected of small and irregular variation of light,
showed remarkable spectral changes in the year
1905,1 somewhat similar to those of a nova, or
temporary star. It is curious that such changes
should occur in a star having an ordinary Sirian
type of spectrum !

A curious quadruple system has been discovered
by Mr. R. T. A. Innes in the southern hemisphere.
The star K Toucani is a binary star with com-
ponents of magnitudes 5 and 7*7, and a period of
revolution of perhaps about 1000 years. Within
6' of this pair is another star (Lacaille 353), which
is also a binary, with a period of perhaps 72
years. Both pairs have the same proper motion
through space, and evidently form a vast quad-
ruple system ; for which Mr. Innes finds a possible
period of 300,000 years.2

It is a curious fact that the performance of a
really good refracting telescope actually exceeds
what theory would indicate ! at least so far as
double stars are concerned. For example, the
famous double-star observer Dawes found that
the distance between the components of a double

1 Seen by Drs. Ludendorff and Eberhard, The Observatory,
April, 190G, p. 166, quoted from Ast. Nach., No. 4067.

2 The Observatory, January, 1907, p, 61.

DOUBLE AND BINARY STARS 169

star which can just be divided, is found by
dividing 4"'56 by the aperture of the object-glass
in inches. Now theory gives 5"*52 divided by
the aperture. " The actual telescope — if a really
good one — thus exceeds its theoretical require-
ments. The difference between theory and
practice in this case seems to be due to the fact
that in the * spurious ' star disc shown by good
telescopes, the illumination at the edges of the
star disc is very feeble, so that its full size is not
seen except in the case of a very bright star '
1 Astronomy and Astrophysics, 1804.

CHAPTER XVI

Variable Stars

IN that interesting work A Cycle of Celestial
Objects, Admiral Smyth says (p. 275),
"Geminiaiio Moiitanari, as far back as 1670,
was so struck with the celestial changes, that he
projected a work to be intituled the Instabilities
of the Firmament, hoping to show such alterations
as would be sufficient to make even Aristotle —
were he alive — reverse his opinion on the incor-
ruptibility of the spangled sky: * There are now
wanting in the heavens,' said he, * two stars
of the 2nd magnitude in the stem and yard of
the ship Argo. I and others observed them in
the year 1664, upon occasion of the comet that
appeared in that year. When they first dis-
appeared I know not ; only I am sure that on
April 10, 1668, there was not the least glimpse of
them to be seen.' " Smyth adds, " Startling as
this account is — and I am even disposed to
question the fact — it must be recollected that
Montanari was a man of integrity, and well
versed in the theory and practice of astronomy ;

VARIABLE STARS 171

and his account of the wonder will be found — in
good set Latin— in page 2202 of the Philosophical
Transactions for 1671."

There must be, I think— as Smyth suggests —
some mistake in Montanari's observations, for it
is quite certain that of the stars mentioned by
Ptolemy (second century A.D.) there is no star of
the 2nd magnitude now missing. It is true that
Al-Sufi (tenth century) mentions a star of the
third magnitude mentioned by Ptolemy in the
constellation of the Centaur (about 2° east of
the star e Centauri) which he could not find. But
this has nothing to do with Montanari's stars..
Montanari's words are very clear. He says,
" Desunt in Ccelo duce stellce Secundse Magnitudinis
in Puppi Navis ejusve Transtris Bayero /? et y,
prope Can em Majoris, a me et aliis9 occasione
prcesertim Cometce A. 1664 observatce et recognitce.
Earum Disparitionem cui Anno debeam, non
novi; hoc indubium, quod a die 10 April, 1668,
ne vestigium quidem illarum adesse amplius
observe ; cceteris circa eas etium, quartos et quintce
magnitudinis, immotis" So the puzzle remains
unsolved.

Sir William Herschel thought that " of all stars
which are singly visible, about one in thirty are
undergoing an observable change." 1 Now taking
the number of stars visible to the naked eye at
6000, this would give about 200 variable stars
1 Smyth's Celestial Cycle, p. 223.

172 ASTRONOMICAL CURIOSITIES

visible at maximum to the unaided vision. But
this estimate seems too high. Taking all the
stars visible in the largest telescopes — possibly
about 100 millions — the proportion of variable
stars will probably be much smaller still.

The theory that the variation of light in the
variable stars of the Algol type is due to a
partial eclipse by a companion star (not neces-
sarily a dark body) is now well established
by the spectroscope, and is accepted by all
astronomers. The late Miss Clarke has well said
" to argue this point would be enforcer une porte
ouverte.

According to Dr. A. W. Roberts, the components
of the following " Algol variables " " revolve in
contact " : V Puppis, X Carinse, /3 Lyrae, and
v Pegasi. Of those V Puppis and /3 Lyrae are
known spectroscopic binaries. The others are
beyond the reach of the spectroscope, owing to
their f aintness.

A very curious variable star of the Algol type
is that known as R R Draconis. Its normal
magnitude is 10, but at minimum it becomes
invisible in a 7J-inch refracting telescope. The
variation must, therefore, be over 3 magnitudes,
that is, at minimum its light must be reduced to
about one-sixteenth of its normal brightness.
The period of variation from maximum to
minimum is about 2*83 days. The variation of
light near minimum is extraordinarily rapid, the

VARIABLE STARS 173

light decreasing by about 1 magnitude in half an
hour.1

A very remarkable variable star has been
recently discovered in the constellation Auriga.
Prof. Hartwig found it of the 9th magnitude on
March 6, 1908, the star " having increased four
magnitudes in one day, whilst within eight days
it was less than the 14th magnitude." 2 In other
words its light increased at least one-hundred-
fold in eight days !

The period of the well-known variable star
/3 Lyrse seems to be slowly increasing. This Dr.
Roberts (of South Africa) considers to be due
to the component stars slowly receding from
each other. He finds that " a very slight increase
of one-thousandth part of the radius of the orbit
would account for the augmentation in time,
30m in a century." According to the theory of
stellar evolution the lengthening of the period
of revolution of a binary star would be due to
the " drag " caused by the tides formed by each
component on the other.3

M. Sebastian Albrecht finds that in the short-
period variable star known as T Vulpeculse (and
other variables of this class, such as Y Ophiuchi),
there can be no eclipse to explain the variation
of light (as in the case of Algol). The star is a
spectroscopic binary, it is true, but the maximum

1 Nature, February 7, 1907. 2 Ibid., March 19, 1908.
3 Popular Astronomy, vol. 15 (1907), p. 9.

174 ASTRONOMICAL CURIOSITIES

of light coincides with the greatest velocity of
approach in the line of sight, and the minimum
with the greatest velocity of recession. Thus the
light curve and the spectroscopic velocity curve
are very similar in shape, but one is like the other
turned upside down. "That is, the two curves
have a very close correspondence in phase in
addition to correspondence of shape and period."

The star now known as W TJrsae Majoris (the
variability of which was discovered by Mtiller
and Kempf in 1902), 'and which lies between the
stars 0 and v of that constellation, has the
marvellously short period of 4 hours (from
maximum to maximum). Messrs. Jordan and
Parkhurst (U.S.A.), find from photographic plates
that the star varies from 7 '24 to 8*17 magnitude."
The light at maximum is, therefore, more than
double the light at minimum. A sun which loses
more than half .its light and recovers it again in
the short period of 4 hours is certainly a curious
and wonderful object.

In contrast with the above, the same astrono-
mers have discovered a star in Perseus which
seems to vary from about the 6th to the 7th
magnitude in the very long period of 7^ years !
It is now known as X Persei, and its position
for 1900 is R.A. 3h 49m 8s, Dec. N. 30° 46', or
about one degree south-east of the star £ Persei.

1 Astrophysical Journal, June, 1907, p. 330.

2 Ibid., vol. 22, p. 172.

VARIABLE STARS 175

It seems to be a variable of the Algol type, as the
star remained constant in light at about the
6th magnitude from 1887 to 1891. It then began
to fade, and on December 1, 1897, it was reduced
to about the 7th magnitude.

On the night of August 20, 1886, Prof. Colbert,
of Chicago, noticed that the star £ Cassiopeiae
increased in brightness " by quite half a magnitude,
and about half an hour afterwards began to
return to its normal magnitude." x This curious
outburst of light in a star usually constant in
brightness is (if true) a very unusual phenomenon.
But a somewhat similar fluctuation of light is
recorded by the famous German astronomer Heis.
On September 26, 1850, he noted that the star
" £ Lyrse became, for a moment, very bright, and
then again faint." (The words in his original
observing book are : " £ Lyrse wurde einen
Moment sehr hell und hierauf wieder dunkel.")
As Heis was a remarkably accurate observer of
star brightness, the above remark deserves the
highest confidence.2

The variable star known as the V Delphini was
found to be invisible in the great 40-inch telescope
of the Yerkes Observatory on July 20, 1900. Its
magnitude was, therefore, below the 17th. At its
maximum brightness it is about 7J, or easily
visible in an ordinary opera-glass, so that its

1 Nature, November 18, 1886.

2 Astrophysical Journal, vol. 17 (1903), p. 282.

176 ASTRONOMICAL CURIOSITIES

range of variation is nearly, or quite, ten magni-
tudes. That is, its light at maximum is about
10,000 times its light at minimum. That a sun
should vary in light to this enormous extent is
certainly a wonderful fact. A variable discovered
by Ceraski (and numbered 7579 in Chandlers'
Catalogue) "had passed below the limit of the
40-inch in June, 1900, and was, therefore, not
brighter than 17 mag." l

The late Sir C. E. Peck and his assistant, Mr.
Grover, made many valuable observations of
variable stars at the Rousden Observatory during
many years past. Among other interesting things
noted, Peck sometimes saw faint stars in the field
of view of his telescope which were at other times
invisible for many months, and he suggested that
these are faint variable stars with a range of
brightness from the 13th to the 20th magnitude.
He adds, " Here there is a practically unemployed
field for the largest telescopes." Considering the
enormous number of faint stars visible on stellar
photographs the number of undiscovered variable
stars must be very large.

Admiral Smyth describes a small star near
|8 Leonis, about 5' distant, of about 8th magnitude,
and dull red. In 1864 Mr. Knott measured a faint
star close to Smyth's position, but estimated it
only 11-6 magnitude. The Admiral's star would
thereupon seem to be variable.2

1 AstrophysicalJournal, vol. 12 (1900), p. 54.

2 Nature, March 21, 1878.

VARIABLE STARS 177

The famous variable star rj Argus, which Sir
John Herschel, when at the Cape of Good Hope in
1838, saw involved in dense nebulosity, was in
April, 1869, "seen on the bare sky," with the
great Melbourne telescope, "the nebula having
disappeared for some distance round it." Other
changes were noticed in this remarkable nebula.
The Melbourne observers saw "three times as
many stars as were seen by Herschel." But of
course their telescope is much larger — 48 inches
aperture, compared with Herschel's 20 inches.

Prof. E. C. Pickering thinks that the fluctuations
of light of the well-known variable star R Coronse
(in the Northern Crown), " are unlike those of
any known variable." This very curious object
— one of the most curious in the heavens — some-
times remains for many months almost constant
in brightness (just visible to the naked eye), and
then rapidly fades in light by several magnitudes !
Thus its changes of light in April and May, 1905,
were as follows : —

1905, April 1 6'0 magnitude

„ 11 7-3 „

„ 12 8-4

Mayl 11-4 „

„ 7 12-5

Thus between April 1 and May 1, its light was
reduced by over 5 magnitudes. In other words,
the light of the star on May 1 was reduced to less
than one-hundredth of its light on April 1. If our

178 ASTRONOMICAL CURIOSITIES

sun were to behave in this way nearly all life
would soon be destroyed on the face of the earth.

M. H. E. Lau finds that the short-period
variable star 8 Cephei varies slightly in colour as
well as in light, and that the colour curve is
parallel to the light curve. Near the minimum of
light the colour is reddish yellow, almost as red
as £ Cephei ; a day later it is pure yellow, and
of about the same colour as the neighbouring
e Cephei.1 But it would not be easy to fully
establish such slight variations of tint.

A remarkably bright maximum of the famous
variable Mira Ceti occurred in 1906. In December
of that year it was fully 2nd magnitude. The
present writer estimated it 1*8, or nearly equal to
the brightest on record — 1'7 observed by Sir
William Herschel and Wargentinin the year 1779.
From photographs of the spectrum taken by Mr.
Slipher at the Lowell Observatory in 1907, he finds
strong indications of the presence of the rather
rare element vanadium in the star's surroundings.
Prof. Campbell finds with the Mills spectrograph
attached to the great 36-inch telescope of the Lick
Observatory that Mira is receding from the earth
at the apparently constant velocity of about 38
miles a second.2 This, of course, has nothing to do
with the variation in the star's light. Prof.
Campbell failed to see any trace of the green line

1 Bulletin, Ast. Soc. de France, June, 1904.

2 Journal, B.A.A., vol. 17 (1903), p. 282.

VARIABLE STARS 179

of hydrogen in the star's spectrum, while two
other lines of the hydrogen series " glowed with
singular intensity."

Mr. Newall has found evidence of the element
titanium in the spectrum of Betelgeuse (a Ori-
onis) ; Mr. Goatcher and Mr. Lunt (of the Cape
Observatory) find tin in Antares (and Scorpii). If
the latter observation is confirmed it will be the
first time this metal has been found in a star's
atmosphere.1

It is a curious fact that Al-Sufi (tenth century)
does not mention the star € Aquilse, which lies
closely north-west of £ Aquilse, as it is now quite
conspicuous to the naked eye. It was suspected of
variation by Sir William Herschel. It was first
recorded by Tycho Brahe about 1590, and he
called it 3rd magnitude. Bayer also rated it 3, and
since his time it has been variously estimated
from 3£ to 4. If it was anything like its present
brightness (4'21 Harvard) in the tenth century it
seems difficult to explain how it could have escaped
Al-Sufi's careful scrutiny of the heavens, unless it
is variable. Its colour seems reddish to me.

Mr. W. T. Lynn has shown— and I think con-
clusively— that the so-called " new star " of A.n.
389 (which is said to have appeared near Altair in
the Eagle) was really a eomet.2

Near the place of Tycho Brahe's great new star

1 Nature, June 20, 1909.

2 The Observatory, vol. 7 (1884), p. 17.

180 ASTRONOMICAL CURIOSITIES

of 1572 (the " Pilgrim Star "), Hind and W. E.
Plummer observed a small star (No. 129 of
d' Arrest's catalogue of the region) which seemed to
show small fluctuations of light, which " scarcely
include a whole magnitude." This may possibly
be identical with Tycho Brahe's wonderful star,
and should be watched by observers. The place
of this small star is (for 1865) R.A. Oh 17m 18s,
N.P.D. 26° 37'*1. The region was examined by
Prof. Burnham in 1890 with the 36-inch telescope
of the Lick Observatory. " None of the faint
stars near the place presented any peculiarity
worthy of remark, but three double stars were
found." l

With reference to the famous Nova (T) Coronse
—the " Blaze Star " of 1866— Prof . Barnard finds
from careful comparisons with small stars in its
vicinity that " the Nova is now essentially of the
same brightness it was before the outburst of
1866 . . . there seems to be no indication of
motion in the Nova"

With reference to the cause of "temporary"
stars, or novce, as they are now called by astro-
nomers— the late Prof. H. C. Vogel said —

" A direct collision of two celestial bodies is not
regarded by Huggins as an admissible explanation
of the Nova ; a partial collision has little proba-
bility, and the most that can be admitted is perhaps
the mutual penetration and admixture of the outer

\The Observatory, Tol. 14 (1891), p. 69.

VARIABLE STARS 181

gaseous envelopes of the two bodies at the time of
their closest approach. A more probable explana-
tion is given by an hypothesis which we owe to
Klinkerfues, and which has more recently been
further developed by Wilsing, viz. that by the very
close passage of two celestial bodies enormous tidal
disturbances are produced and thereby changes in
the brightness of the bodies. In the case of the
two bodies which form the Nova, it must be
assumed that these phenomena are displayed in
the highest degree of development, and that
changes of pressure have been produced which
have caused enormous eruptions from the heated
interior of the bodies ; the eruptions are perhaps
accompanied by electrical actions, and are com-
parable with the outbursts in our own sun,
although they are on a much larger scale." l

It will be noticed that this hypothesis agrees
with the fundamental assumption of the " Planet-
esimal Hypothesis " advocated by Professors
Chamberlin and Moulton (see my Astronomical
Essays, p. 324).

The rush of a comparatively small body through
a mass of gaseous matter seems also a very
plausible hypothesis. This idea was originally
advanced by Prof. Seeliger, and independently by
Mr. Monck.

With reference to the nebula which was
observed round the great new star of 1901 — Nova
Persei — Prof. Lewis Bell supports the theory of
Seeliger, which accounts for the apparent move-
ments of the brightest portions of the nebula by
1 Astronomy and Astrophysics, 189G, p. 54.

182 ASTRONOMICAL CURIOSITIES

supposing that the various parts of the highly
tenuous matter were successively lighted up by
the effects of a travelling electro-magnetic wave-
front, and he shows that this theory agrees well
with the observed phenomenon.1 The " collision
theory " which explained the sudden outburst of
light by the meeting of two dark bodies in space,
seems to be now abandoned by the best astro-
nomers. The rapid cooling down of the supposed
bodies indicated by the rapid decrease of light is
quite inconsistent with this hypothesis.

The rapid diminution in the light of some of
these " new stars " is very remarkable. Thus the
new star which suddenly blazed out near the
nucleus of the great nebula in Andromeda in
August, 1885, faded down in 5 months from " the
limit of visibility to the naked eye to that of a
26-inch telescope " ! A large body could not cool
in this way.

Mr. Harold K. Palmer thinks that the " complete
and astonishingly rapid changes of spectral type
observed in the case of Nova Cygni and Nova
Aurigce, and likewise those observed in Nova
Normce, Nova Sagittarii and Nova Persei, leave
little doubt that the masses of these objects are
small." 2

No less than 3748 variable stars had been
discovered up to May, 1907. Of these 2909 were

1 Nature, August 28, 1902.

2 Astrophysical Journal, October, 1903.

VARIABLE STARS 183

found at Harvard Observatory (U.S.A.) chiefly
by means of photography.1

The star 14. 1904 Cygni has a period of only
3 hours 14 minutes, which is the shortest period
known for a variable star.

A very interesting discovery has recently been
made with reference to the star p Herculis. It has
been long suspected of variable light with a period
of 35 or 40 days, or perhaps irregular. Frost and
Adams now find it to, be a spectroscopic binary,
and further observations at Harvard Observatory
show that it is a variable of the Algol (or perhaps
ft Lyrae) type. The Algol variation of light was
suggested by MM. Baker and Schlesinger. The
period seems to be about 2*05 days.2

The northern of the two " pointers " in the
Plough (so called because they nearly point to the
Pole Star) is about the 2nd magnitude, as Al-
Sufi rated it. It was thought to be variable in
colour by Klein, Konkoly, and Weber ; and M.
Lau has recently found a period of 50 days
with a maximum of "jaune rougeatre " on April 2>
1902.

The famous variable star 17 Argus did "not
exceed the 8th magnitude" in February, 1907,
according to Mr. Tebbutt.3 This is the faintest
ever recorded for this wonderful star.

1 Nature, May 30, 1907.

2 Popular Astronomy, February, 1909, p. 125.
s Tlw Observatory, May, 1907, p. 21G.

184 ASTRONOMICAL CURIOSITIES

It is stated in Knowledge (vol. 5, p. 3,
January 4, 1884) that the temporary star of 1876
(in the constellation of Cygnus) " had long been
known and catalogued as a telescopic star of the
9th magnitude with nothing to distinguish it from
the common herd." But this is quite erroneous.
The star was quite unknown before it was dis-
covered by Schmidt at Athens on November 24
of that year. The remark apparently refers to
the " Blaze Star " of 1866 in Corona Borealis, which
was known previously as a star of about the 9th
magnitude before its sudden outburst on May
12 of that year.

This "new star" of 1866 — T Coronse, as it is
now called— was, with the possible exception of
Nova Persei (1901), the only example of a nova
which was known to astronomers as a small star
previous to the great outburst of light. It is the
brightest of the novce still visible. It was the
first of these interesting objects to be examined
with the spectroscope. It was observed by
Burnham in the years 1904-1906 with the great
40-inch telescope of the Yerkes Observatory
(U.S.A.). He found its colour white, or only
slightly tinged with yellow. In August and
September, 1906, he estimated its magnitude at
about 9*3, and " it would seem therefore that the
Nova is now essentially of the same brightness it
was before the outburst in 1866." It shows
no indication of motion. Burnham found no

VARIABLE STARS 185

peculiarity about its telescopic image. A small
and very faint nebula was found by Burnham a
little following (that is east of) the nova.1

The following details of the great new star of
1572— the "Pilgrim Star" of Tycho Brahe— are
given by Delambre.2 In November, 1572, it was
brighter than Sirius, Vega, and Jupiter, and
almost equal to Venus at its brightest. During
December it resembled Jupiter in brightness. In
January, 1573, [it was fainter and only a little
brighter than stars of the 1st magnitude. In
February and March it was equal to 1st magni-
tude stars,"and in April and May was reduced to
the 2nd magnitude. In June and July it was
3rd magnitude; in September of the 4th, and at
the end of 1573 it was reduced to the 5th magni-
tude. In February, 1574, it was 6th magnitude,
and in March of the same year it became invisible
to the naked eye.

From this account it will be seen that the
decrease in light of this curious object was much
slower than that of Nova Persei (1901) (" the new
star of the new century"). This would suggest
that it was a much larger body.

There were also changes in its colour. When
it was of the brightness of Venus or Jupiter it
shone with a white light. It then became golden,
and afterwards reddish like Mars, Aldebaran, or

1 Astropliysical Journal, May, 1907.

2 Histoire de V Astronomic Moderne, vol. i. pp. 1S5-G.

186 ASTRONOMICAL CURIOSITIES

Betelgeuse. It afterwards became of a livid white
colour like Saturn, and this it retained as long as
it was visible. Tycho Brahe thought that its
apparent diameter might have been about 3^
minutes of arc, and that it was possibly 361 times
smaller than the earth (!) But we now know that
these estimates were probably quite erroneous.

Temporary stars were called by the ancient
Chinese " Ke-sing," or guest stars.1

A temporary star recorded by Ma-tuan-lin
(Chinese Annals) in February, 1578, is described as
" a star as large as the sun." But its position is
not given.3

About the middle of September, 1878, Mr. Greely,
of Boston (U.S.A.), reported to Mr. E. P. Sawyer
(the eminent'observer of variable stars) that, about
the middle of August of that year, he had seen the
famous variable star Mira Ceti of about the 2nd
magnitude, although the star did not attain its
usual maximum until early in October, 1878. Mr.
Greely stated that several 'nights after he first
saw Mira it had faded to the 4th or 5th magnitude.
If there was no mistake in this observation (and
Sawyer could find none) it was quite an unique
phenomenon, as nothing of the sort has been
observed before or since in the history of this
famous star. It looks as if Mr. Greely had
observed a new or " temporary " star near the

1 Humboldt'B Cosmos, vol. iii. p. 210 (Otte's translation).

2 Ibid., vol. iii. pp. 213-14.

VARIABLE STARS 187

place of Mira Ceti; but as the spot is far from
the Milky Way, which is the usual seat of such
phenomena, this hypothesis seems improbable.

In the so-called Cepheid and Geminid variables
of short period, the principal characteristics of
the light variation are as follows : —

" 1. The light varies without pause.

" 2. The amount of their light variation is
usually about 1 magnitude.

" 3. Their periods are short — a few days only.

" 4. They are of a spectral type approximately
solar ; no Orion, Sirian or Arcturian stars having
been found among them.

" 5. They seem to be found in greater numbers
in certain parts of the sky, notably in the Milky
Way, but exhibit 110 tendency to form clusters.

" 6. All those stars whose radial velocities have
been studied have been found to be binaries whose
period of orbital revolution coincides with that of
their light change.

" 7. The orbits, so far as determined, are all
small, a sin i being 2,000,000 kilometres or less.

"8. Their maximum light synchronizes with
their maximum velocity of approach, and mini-
mum light with maximum velocity of recession.

" 9. No case has been found in which the
spectrum of more than one component has been
bright enough to be recorded in the spectro-
grams." l

It is very difficult to find an hypothesis which

will explain satisfactorily all these characteristics,

and attempts in this direction have not proved

very successful. Mr. J. C. Duncan suggests the

1 J. C. Duncan, LicJs Observatory Bulletin, No. 151.

188 ASTRONOMICAL CURIOSITIES

action of an absorbing atmosphere surrounding
the component stars.

On March 30, 1612, Schemer saw a star near
Jupiter. It was at first equal in brightness to
Jupiter's satellites. It gradually faded, and on
April 8 of the same year it was only seen with
much difficulty in a very clear sky. " After that
date it was never seen again, although carefully
looked for under favourable conditions."

An attempted identification of Schemer's star
was made in recent years by Winnecke. He found
that its position, as indicated by Schemer, agrees
with that of the Bonn Durchmusterung star 15°,
2083 (8J magnitude). This star is not a known
variable. Winnecke watched it for 17 years, but
found 110 variation of light. From Schemer's
recorded observations his star seems to have
reached the 6th magnitude, which is considerably
brighter than the Durchmusterung star watched
by Winnecke.1

With reference to the colours of the stars, the
supposed change of colour in Sirius from red to
white is well known, and will be considered in the
chapter on the Constellations. The bright star
Arcturus has also been suspected of variation in
colour. About the middle of the nineteenth century
Dr. Julius Schmidt, of Athens, the well-known
observer of variable stars, thought it one of the
reddest stars in the sky, especially in the year
1 A*tropJ>ysical Journal, vol. 17, p. 283.

VARIABLE STARS 189

1841, when he found its colour comparable with
that of the planet Mars.1 In 1852, however, he
was surprised to find it yellow and devoid of any
reddish tinge ; in colour it was lighter than that
of Capella. In 1863, Mr. Jacob Ennis found it
"decidedly orange." Ptolemy and Al-Sufi called
it red.

Mr. Ennis speaks of Capella as " blue " (classing
it with Rigel), and comparing its colour with that
of Vega ! 2 But the present writer has never seen
it of this colour. To his eye it seems yellowish or
orange. It was called red by Ptolemy, El Pergani,
and Riccioli ; but Al-Sufi says nothing about its
colour.

Of /3 Ursae Minoris, Heis, the eminent German
astronomer said, "I have had frequent oppor-
tunities of convincing myself that the colour of
this star is not always equally red ; at times it is
more or less yellow, at others most decidedly
red." 3

Among double stars there are many cases in
which variation of colour has been suspected. In
some of these the difference in the recorded colour
may possibly be due to " colour blindness " in some
of the observers ; but in others there seems to be
good evidence in favour of a change. The follow-
ing may be mentioned : —

1 The Origin of the Stars, p. 143.

2 Ibid., p. 135.

3 Quoted by Ennis in The Origin of the Stars, p. 133.

190 ASTRONOMICAL CURIOSITIES

rj Cassiopeise. Magnitudes of the components
about 4 and 7J. Recorded as red and green by
Sir John Herschel and South ; but yellow and
orange by Sestini.

i Trianguli. Magnitudes 5| and 7. Secchi esti-
mated them as white or yellow and blue ; but
Webb called them yellow and green (1862).

y Leonis, 2 and 3£. Sir William Herschel noted
them white and reddish white ; but Webb, light
orange and greenish yellow.

12 Canum Venaticorum, 2J and 6*. White and
red, Sir William Herschel ; but Sir John Herschel
says in 1830, " With all attention I could perceive
no contrast of colours in the two stars." Struve
found them both white in 1830, thus agreeing with
Sir John Herschel. Sestini saw them yellow and
blue in 1844 ; Smyth, in 1855, pale reddish white
and lilac ; Dembowski, in 1856, white and pale
olive blue ; and Webb, in 1862, flushed white and
pale lilac.

On October 13, 1907, Nova Persei, the great new
star of 1901, was estimated to be only 11*44
magnitude, or about 11|. When at its brightest
this famous star was about zero magnitude ; so
that it has in about 6 years faded about 11{T
magnitudes in brightness ; in other words, it has
been reduced to ^-—-3 of its greatest brilliancy !

CHAPTER XVII

Nebulae and Clusters

IN his interesting and valuable work on "The
Stars," the late Prof. Newcomb said —

"Great numbers of the nebulae are there-
fore thousands of times the dimensions of the
earth's orbit, and most of them are thousands
of times the dimensions of the whole solar
system. That they should be completely trans-
parent through such enormous dimensions shows
their extreme tenuity. Were our solar system
placed in the midst of one of them] it is probable
that we should not be able to find any evidence
of its existence " !

Prof. Perrine thinks that the total number of
the nebulas will ultimately be found to exceed a
million.1

Dr. Max Wolf has discovered a number of small
nebulae in the regions near Algol and Nova Persei
(the great "new star" of 1901). He says, "They
mostly lie in two bands," and are especially
numerous where the two bands meet, a region
of 12 minutes of arc square containing no less
than 148 of them. They are usually " round with
1 Astroplty steal Journal, vol. 20 (1904), p. 357.

192 ASTRONOMICAL CURIOSITIES

central condensation," and form of Andromeda
nebula.1

Some small nebulae have been found in the
vicinity of the globular clusters. They are
described by Prof. Perrine as very small and like
an " out of focus " image of a small star. " They
appear to be most numerous about clusters which
are farthest from the galaxy." Prof. Perrine
says, " Practically all the small nebulae about the
globular clusters are elliptical or circular. Those
large enough to show structure are spirals. Doubt-
less the majority of these are spirals."2 This
seems further evidence in favour of the "spiral
nebular hypothesis" of Chamberlin and Moulton.

A great photographic nebula in Orion was
discovered by Prof. Barnard in 1894. In a draw-
ing he gives of the nebula,3 it forms a long streak
beginning a little south of y Orionis (Bellatrix),
passing through the star 38 Orionis north of 51
and south of 56 and 60 Orionis. Then turning
south it sweeps round a little north of K Orionis ;
then over 29 Orionis, and ends a little to the west
of rj Orionis. There is an outside patch west of
Rigel. Barnard thinks that the whole forms a
vast spiral structure; probably connected with
the " great nebula " in the " sword of Orion,"
which it surrounds.

1 Nature, March 8,' 1906.

2 Astronomical Society of the Pacific, August, 1908.

3 Astronomy and Astrophysics, 1894, p. 812.

NEBULA AND CLUSTERS 193

From calculations of the brightness of surface
(" intrinsic brightness ") of several " planetary "
nebulae made by the present writer in the year
1905, he finds that the luminosity is very small
compared with that of the moon. The brightest
of those examined (h 3365, in the southern hemi-
sphere, near the Southern Cross) has a surface
luminosity of only ~ of that of the moon.1 The
great nebulae in Orion and Andromeda seem to
have " still smaller intrinsic brightness."

Arago says —

"The spaces which precede or which follow
simple nebulae, and a fortiori groups of nebulae,
contain generally few stars. Herschel found this
rule to be invariable. Thus every time that,
during a short interval, no star appeared, in
virtue of the diurnal motion, to place itself in the
field of his motionless telescope, he was accustomed
to say to the secretary who assisted him (Miss
Caroline Herschel), ' Prepare to write ; nebulae are
about to arrive.' " 2

Commenting on this remark of Arago, the late
Herbert Spencer says —

" How does this fact consist with the hypothesis
that nebulae are remote galaxies ? If there were
but one nebula, it would be a curious coincidence
were this one nebula so placed in the distant
regions of space as to agree in direction with a
starless spot in our sidereal system ! If there
were but two nebulae, and both were so placed,
the coincidence would be excessively strange.

1 The Observatory, May, 1905.

2 This is a misquotation. See my Astronomical Essays, p. 185.

194 ASTRONOMICAL CURIOSITIES

What shall we say on finding that they are
habitually so placed ? (the last five words replace
some that are possibly a little too strong). . . .
When to the fact that the general mass of nebulae
are antithetical in position to the general mass of
the stars, we add the fact that local regions of
nebulae are regions where stars are scarce, and
the further fact that single nebulae are habitually
found in comparatively starless spots, does not
the proof of a physical connection become over-
whelming?"1

With reference to the small elongated nebula
discovered by Miss Caroline Herschel in 1783 near
the great nebula in Andromeda, Admiral Smyth
says, "It lies between two sets of stars, consist-
ing of four each, and each disposed like the
figure 7, the preceding group being the smallest." 2

Speaking of the " nebula " Messier 3 — a globular
cluster in Canes Venatici — Admiral Smyth says,
" This mass is one of those balls of compact and
wedged stars whose laws of aggregation it is so
impossible to assign ; but the rotundity of the figure
gives full indication of some general attractive
bond of union." 3 The terms " compact and
wedged" are, however, too strong, for we know
that in the globular clusters the component stars
must be separated from each other by millions of
miles !

Prof. Chamberlin suggests that the secondary
nebula (as it is called) in the great spiral in Canes

1 Nature, February 3, 1870.
- Bedford Catalogue, p. 14. ,3 Ibid., p. 307.

NEBULA AND CLUSTERS 195

Venaticij' (Messier ] 51) may possibly represent
the body which collided with the other (the
chief nucleus) in a grazing collision, and is now
escaping. He considers this secondary body to
have been " a dead sun " — that is,' a dark body.1
This would be very interesting if it could be
proved. But it seems to me more probable that
the secondary nucleus is simply a larger portion
of the ejected matter, which is now being
gradually detached from the parent mass.

Scheiner says "the previous suspicion that
the spiral nebulae are star clusters is now raised
to a certainty," and that the spectrum of the
Andromeda nebula is very similar to that of the
sun. He says there is "a surprising agreement
of the two, even in respect to the relative intensity
of the separate spectral regions." 2

In the dynamical theory of spiral nebulae, Dr.
E. J. Wilczynski thinks that the age of a spiral
nebula may be indicated by the number of its
coils ; those having the largest number of coils
being the oldest, from the point of view of
evolution.3 This seems to be very probable.

In the spectrum of the gaseous nebula?, the F
line of hydrogen (H/3) is visible, but not the C
line (Ha). The invisibility of the C line is ex-
plained by Scheiner as due to a physiological

1 Astrophysical Journal, vol. 14, p. 37.

2 Ibid., vol. 9, p. 149.

3 Nature, July 20, 1899.

196 ASTRONOMICAL CURIOSITIES

cause, " the eye being less sensitive to that part of
the spectrum in which the line appears than to
the part containing the F line." l

An apparent paradox is found in the case of the
gaseous nebulae. The undefined outlines of these
objects render any attempt at measuring their
parallax very difficult, if not impossible. Their
distance from the earth is therefore unknown,
and perhaps likely to remain so for many years
to come. It is possible that they may not be
farther from us than some of the stars visible
in their vicinity. On the other hand, they may
lie far beyond them in space. But whatever
their distance from the earth may be, it may
be easily shown that their attraction on the sun
is directly proportioned to their distance — that
is, the greater their distance, the greater the
attraction! This is evidently a paradox, and
rather a startling one too. But it is nevertheless
mathematically true, and can be easily proved.
For, their distance being unknown, they may be
of any dimensions. They might be comparatively
small bodies relatively near the earth, or they
may be immense masses at a vast distance from
us. The latter is, of course, the more probable.
In either case the apparent size would be the
same. Take the case of any round gaseous
nebula. Assuming it to be of a globular form,
its real diameter will depend on its distance from
1 Ast. Nach., No. 3476.'

NEBULA AND CLUSTERS 197

the earth — the greater the distance, the greater
the diameter. Now, as the volumes of spheres
vary as the cubes of their diameters, it follows
that the volume of the nebula will vary as the
cube of its distance from the earth. As the mass
of an attracting body depends on its volume and
density, its real mass will depend on the cube of
its distance, the density (although unknown)
being a fixed quantity. If at a certain distance
its mass is m, at double the distance (the apparent
diameter being the same) it would have a mass
of eight times m (8 being the cube of 2), and at
treble the distance its mass would be 27 m, and
so on, its apparent size being known, but not its
real size. This is obvious. Now, the attractive
power of a body varies directly as its mass —
the greater the mass, the greater the attraction.
Again, the attraction varies inversely as the
square of the distance, according to the well-
known law of Newton. Hence if d be the un-
known distance of the nebula, we have its
attractive power varying as d3 divided by d\
or directly as the distance d. We have then the
curious paradox that for a nebula whose distance
from the earth is unknown, its attractive power
on the sun (or earth) will vary directly as the
distance — the greater the distance the greater the
attraction, and, of course, conversely, the smaller
the distance the less the attractive power. This
result seems at first sight absurd and incredible,

198 ASTRONOMICAL CURIOSITIES

but a little consideration will show that it is quite
correct. Consider a small wisp of cloud in our
atmosphere. Its mass is almost infinitesimal and
its attractive power on the earth practically nil.
But a gaseous nebula having the same apparent
size would have an enormous volume, and,
although probably formed of very tenuous gas,
its mass would be very great, and its attractive
power considerable. The large apparent size of
the Orion nebula shows that its volume is probably
enormous, and as its attraction on the sun is not
appreciable, its density must be excessively small,
less than the density of the air remaining in the
receiver of the best air-pump after the air has
been exhausted. How such a tenuous gas can
shine as it does forms another paradox. Its
light is possibly due to some phosphorescent or
electrical action.

The apparent size of "the great nebula in
Andromeda " shows that it must be an object of
vast dimensions. The nearest star to the earth,
Alpha Centauri, although probably equal to our
sun in volume, certainly does not exceed one-
hundredth of a second in diameter as seen from
the earth. But in the case of the Andromeda
nebula we have an object of considerable apparent
size, not measured by seconds of arc, but showing
an area about three times greater than that
of the full moon. The nebula certainly lies in
the region of the stars — much farther off than

NEBULA AND CLUSTERS 199

Alpha Centauri — and its great apparent size shows
that it must be of stupendous dimensions. A
moment's consideration will show that whatever
its distance may be, the farther it is from the
earth the larger it must be in actual size. The
sun is vastly larger than the moon, but its
apparent size is about the same owing to its
greater distance. Sir William Herschel thought
the Andromeda nebula to be "undoubtedly the
nearest of all the great nebulae," and he estimated
its distance at 2000 times the distance of Sirius.
This would not, however, indicate a relatively
near object, as it would imply a " light journey "
of over 17,000 years! (The distance of Sirius is
about 88 " light years.")

It has been generally supposed that this great
nebula lies at a vast distance from the earth,
possibly far beyond most of the stars seen in the
same region of the sky; but perhaps not quite
so far as HerscheFs estimate would imply.
Recently, however, Prof. Bohlin of Stockholm has
found from three series of measures made in
recent years a parallax of O"'!?.1

This indicates a distance of 1,213,330 times the
sun's distance from the earth, and a "light
journey" of about 19 years. This would make
the distance of the nebula more than twice the
distance of Sirius, about four times the distance
of a Centauri, but less than that of Capella.
1 AstronomiscJie Nachrichten, No. 4213.

200 ASTRONOMICAL CURIOSITIES

Prof. Bohlin's result is rather unexpected, and
will require confirmation before it can be accepted.
But it will be interesting to inquire what this
parallax implies as to the real dimensions and
probable mass of this vast nebula. The extreme
length of the nebula may be taken to represent
its diameter considered as circular. For, although
a circle seen obliquely is always foreshortened
into an ellipse, still the longer axis of the ellipse
will always represent the real diameter of the
circle. This may be seen by holding a penny at
various angles to the eye. Now, Dr. Roberts found
that the apparent length of the Andromeda nebula
is 2| degrees, or 84:00 seconds of arc. The diameter
in seconds divided by the parallax will give the
real diameter of the nebula in terms of the sun's
distance from the earth taken as unity. Now,
8400 divided by 0"'17 gives nearly 50,000, that is,
the real diameter of the Andromeda nebula would
be — on Bohlin's parallax — nearly 50,000 times the
sun's distance from the earth. As light takes
about 500 seconds to come from the sun to the
earth, the above figures imply that light would
take about 290 days, or over 9 months to cross the
diameter of this vast nebula.

Elementary geometrical considerations will show
that if the Andromeda nebula lies at a greater
distance from the earth than that indicated by
Bohlin's parallax, its real diameter, and therefore
its volume and mass, will be greater. If, therefore,

NEBULAE AND CLUSTERS 201

we assume the parallax found by Bolilin, we shall
probably find a minimum value for the size and
mass of this marvellous object.

Among Dr. Roberts' photographs of spiral
nebulae (and the Andromeda nebula is un-
doubtedly a spiral) there are some which are
apparently seen nearly edgeways, and show that
these nebulae are very thin in proportion to their
diameter. From a consideration of these photo-
graphs we may, I think, assume a thickness of
about one-hundredth of the diameter. This would
give a thickness for the Andromeda nebulae of
about 500 times the sun's distance from the earth.
This great thickness will give some idea of the
vast proportions of the object we are dealing
with. The size of the whole solar system — large
as it is — is small in comparison. The diameter
and thickness found above can easily be converted
into miles, and from these dimensions the actual
volume of the nebula can be compared with that
of the sun. It is merely a question of simple
mensuration, and no problem of " high mathe-
matics " is involved. Making the necessary calcu-
lations, I find that the volume of the Andromeda
nebula would be about 2*32 trillion times
(2*32 x 1018) the sun's volume ! Now, assuming that
the nebulous matter fills only one-half of the
apparent volume of the nebula (allowing for
spaces between the spiral branches), we have the
volume = 1'16 x 1018. If the nebula had the same

202 ASTRONOMICAL CURIOSITIES

density as the sun, this would be its mass in terms
of the sun's mass taken as unity, a mass probably
exceeding the combined mass of all the stars visible
in the largest telescopes ! But this assumption
is, of course, inadmissible, as the sun is evidently
quite opaque, whereas the nebula is, partially at
least, more or less transparent. Let us suppose
that the nebula has a mean density equal to that
of atmospheric air. As water is about 773 times
heavier than air, and the sun's density is 1*4
(water = 1) we have the mass of the nebula equal
to 1-16 X 1018 divided by 773 x|l'4, or about 1015
times the sun's mass, which is still much greater
than the probable combined mass of all the visible
stars. As it seems unreasonable to suppose that
the mass of an individual member of our sidereal
system should exceed the combined mass of the
remainder of the system, we seem compelled to
further reduce the density of the Andromeda
nebula. Let us assume a mean density of, say, a
millionth of hydrogen gas (a sufficiently low
estimate) which is about 14*44 times lighter than
air, and we obtain a mass of about 8 x 107 or 80
million times the mass of the sun, which is still an
enormous mass.

As possibly 1 may have assumed too great a
thickness for the nebula, let us take a thickness of
one-tenth of that used above, or one thousandth
of the length of the nebula. This gives a mass
of 8 million times the sun's mass. This seems

NEBULA AND CLUSTERS 203

a more probable mass if the nebula is — as
Bohlin's parallax implies — a member of our sidereal
system.

If we assume a parallax of say 0"'01 — or one-
hundredth of a second of arc — which would still
keep the nebula within the bounds of our sidereal
system — we have the dimensions of the nebula
increased 17 times, and hence its mass nearly 5000
times greater (173) than that found above. The
mass would then be 40,000 million times the sun's
mass ! This result seems highly improbable, for
even this small parallax would imply a light
journey of only 326 years, .whereas the distance
of the Milky Way has been estimated by Prof.
Newcomb at about 3000 years' journey for light.

In Dr. Roberts' photograph many small stars
are seen scattered over the surface of the nebula ;
but these do not seem to be quite so numerous as
in the surrounding sky. If the nebula lies nearer
to us than the fainter stars visible 011 the photo-
graph, some of them may be obscured by the
denser portions of the nebula ; some may be visible
through the openings between the spiral branches ;
while others may be nearer to us and simply pro-
jected on the nebula.

To add to the difficulty of solving this celestial
problem, the spectroscope shows that, the Andro-
meda nebula is not gaseous. The spectrum is,
according to Schemer, very similar to that of
the sun, and " there is a surprising agreement of

204 ASTRONOMICAL CURIOSITIES

the two, even in respect to the relative intensities
of the separate spectral regions."1 He thinks
that " the greater part of the stars comprising
the nucleus of the nebula belong to the second
spectral class" (solar), and that the nebula "is
now in an advanced stage of development. No
trace of bright nebular lines are present, so that
the interstellar space in the Andromeda nebula,
just as in our stellar system, is not appreciably
occupied by gaseous matter." l He suggests that
the inner part of the nebula [the " nucleus "]
" corresponds to the complex of those stars which
do not belong to the Milky Way, while the latter
corresponds to the spirals of the Andromeda
nebula." l On this view of the matter we may
suppose that the component particles are small
bodies widely separated, and in this way the mean
density of the Andromeda nebula may be very
small indeed. They cannot be large bodies, as
he largest telescopes have failed to resolve the
nebula into stars, and photographs show no sign
of resolution.

It has often been suggested, and sometimes
definitely stated, that the Andromeda nebula may
possibly be an " external " universe, that is an
universe entirely outside our sidereal system, and
comparable with /it in size. Let us examine the
probability of such hypothesis. Assuming that
the nebula has the same diameter as the Milky
1 Attropliyncal Journal, vol. 9, p. 149.

NEBULA AND CLUSTERS 205

Way, or about 6000 "light years," as estimated
by Prof. Newcomb, I find that its distance from
the earth would be about 150,000 "light years."
As this is about 8000 times the distance indicated
by Bohlin's parallax, its dimensions would be
8000 times as great, and hence its volume and mass
would be 8000 cubed, or 512,000,000,000 times
greater than that found above. That is, about 4
trillion (4 x 1018) times the sun's mass ! As this
appears an incredibly large mass to be compressed
into a volume even so large as that of our sidereal
system, we seem compelled to reject the hypothesis
that the nebula represents an external universe.
The sun placed at the distance corresponding to
1 50,000 light years would, I find, shine as a star of
less than the 23rd magnitude, a magnitude which
would be invisible in the largest telescope that
man could ever construct. But the combined
light of 4 trillion of stars of even the 23rd magni-
tude would be equal to one of minus 23*5 magni-
tude, that is, 23J magnitude brighter than the
zero magnitude, or not very much inferior to the
sun in brightness. As the Andromeda nebula
shines only as a star of about the 5th magnitude
the hypothesis of an external universe seems to
be untenable.

It is evident, however, that the mass of the
Andromeda nebula must be enormous ; and if it
belongs to our sidereal system, and if the other
great nebulee have similar masses, it seems quite

206 ASTRONOMICAL CURIOSITIES

possible that the mass of the visible universe may
much exceed that of the visible stars, and may be
equal to 1000 million times the sun's mass— as
supposed by the late Lord Kelvin— or even much
more.

With reference to the small star which sud-
denly blazed out near the nucleus of the Andro-
meda nebula in August, 1885, Prof. Seeliger has
investigated the decrease in the light of the star
on the hypothesis that it was a cooling body
which had suddenly been raised to an intense
heat by the shock of a collision, and finds a fair
agreement between theory and observation.
Prof. Auwers points out the similarity between
this outburst and that of the "temporary star"
of 1860, which appeared in the cluster 80 Messier,
and he thinks it very probable that both phe-
nomena were due to physical changes in the
nebulae in which they appeared.

The appearance of this temporary star in the
Andromeda nebula seems to afford further evi-
dence against the hypothesis of the nebula being
an external universe. For, as I have shown above,
our sun, if placed at a distance of 150,000 light
years, would shine only as a star of the 23rd
magnitude, or over 15 magnitudes fainter than
the temporary star. This would imply that the
star shone with a brightness of over a million
times that of the sun, and would therefore
indicate a body of enormous size. But the rapid

NEBULAE AND CLUSTERS 207

fading of its light would, 011 the contrary, imply
a body of comparatively small dimensions. We
must, therefore, conclude that the nebula, what-
ever it may be, is not an external universe, but
forms a member of our own sidereal system,

In Sir John Herschel's catalogue of Nebulae and
Clusters of Stars, published in 1833, in the Philo-
sophical Transactions of the Royal Society, there
are many curious objects mentioned. Of these I
have selected the following : —

No. 496 is described as " a superb cluster which
fills the whole field ; stars 9, 10 . . . 13 magnitude
and none below, but the whole ground of the sky
on which it stands is singularly dotted over with
infinitely minute points." This is No. 22 of Sir
William Herschel's 6th class, and will be found
about 3 degrees south and a little east of the
triple star 29 Monocerotis.

No. 650. This object lies about 3 degrees north
of the star ft Leonis, the most northern of the
bright stars in the well-known " Sickle," and is
thus described by Sir John Herschel : " A star 12th
magnitude with an extremely faint nebulous
atmosphere about 10" to 12". It is between a star
8-9 magnitude north preceding, and one 10th
magnitude south following, neither of which are
so affected. A curious object."

No. 1558. Messier 53. A little north-east of
the star a Comae Berenices. Described as "a
most beautiful highly compressed cluster. Stars

208 ASTRONOMICAL CURIOSITIES

very small, 12th . . . 20tli magnitude, with scat-
tered stars to a considerable distance ; irregularly
round, but not globular. Comes up to a blaze in
the centre ; indicating a round mass of pretty
equable density. Extremely compressed. A most
beautiful object. A mass of close-wedged stars
5' in diameter ; a few 12th magnitude, the rest of
the smallest size and innumerable." Webb says,
" Not very bright with S~ inches ; beautiful with
9 inches." This should be a magnificent object
with a very large telescope, like the Lick or
Yerkes.

No. 2018. "A more than usually condensed
portion of the enormous cluster of the Milky
Way. The field has 200 or 300 stars in it at
once." This lies about 2° south-west of the star
6 Aquilse, which is near the northern edge of
the bright spot of Milky Way light in "Sobi-
eski's Shield " — one of the brightest spots in the
sky.

No. 2093. " A most wonderful phenomenon. A
very large space 20' or 30' broad in Polar Distance,
and lm or 2m in Right Ascension, full of nebula
and stars mixed. The nebula is decidedly attached
to the stars, and is as decidedly not stellar. It
forms irregular lace-work marked out by stars,
but some parts are decidedly nebulous, wherein
no star can be seen." Sir John Herschel gives a
figure of this curious spot, which he says repre-
sents its " general character, but not the minute

NEBULAE AND CLUSTERS 209

details of this object, which would be extremely
difficult to give with any degree of fidelity." It
lies about 3 degrees west of the bright star
£ Cygni.

Among the numerous curious objects observed
by Sir John Herschel during his visit to the Cape
of Good Hope, the following may be mentioned : —

h 2534 (H iv. 77). Near r4 Eridani. Sir John
Herschel says, "Attached cometically to a 9th
magnitude star which forms its head. It is an
exact resemblance to Halley's comet as seen in a
night glass." ... "A complete telescopic comet;
a perfect miniature of Halley's comet, only the
tail is rather broader in proportion." 1

h 3075. Between y Monocerotis and y Canis
Majoris. " A very singular nebula, and much like
the profile of a bust (head, neck, and shoulders)
or a silhouette portrait, very large, pretty well
defined, light nearly uniform, about 12' diameter.
In a crowded field of Milky Way stars, many of
which are projected on it.2

h 3315 (Dunlop 323). In the Milky Way;
about 3° east of the Eta Argus nebula. Sir John
Herschel says, "A glorious cluster of immense
magnitude, being at least 2 fields in extent every
way. The stars are 8, 9, 10, and llth magnitudes,
but chiefly 10th magnitude, of which there must
be at least 200. It is the most brilliant object of
the kind I have ever seen " . . . " has several
» Cape Observations, p. 61. 2 Ibid., p. 85.

210 ASTRONOMICAL CURIOSITIES

elegant double stars, and many orange-coloured
stars." l This should form a fine object in even
a comparatively small telescope, and may be
recommended to observers in the southern hemi-
sphere. A telescope of 3-inches aperture should
show it well.

Among astronomical curiosities may be counted
" clusters within clusters." A cluster in Gemini
(N.G.C. 2331) has a small group of " six or seven
stars close together and well isolated from the
rest."

Lord Rosse describes No. 4511 of Sir John
Herschel's General Catalogue of Nebulae and
Clusters (Phil. Trans., 1864) as " a most gorgeous
cluster, stars 12-15 magnitude, full of holes." 2
His sketch of this cluster shows 3 rings of stars
in a line, each ring touching the next on the out-
side. Sir John Herschel described it as " Cluster ;
very large; very rich; stars 11-15 magnitude
(Harding, 1827)," but says nothing about the rings.
This cluster lies about 5 degrees south of 8 Cygni.

Dr. See, observing with the large telescope of
the Lowell Observatory, found that when the
sky is clear, the moon absent, and the seeing
perfect, " the sky appeared in patches to be of a
brownish colour," and suggests that this colour
owes its existence to immense cosmical clouds,
which are shining by excessively feeble light!

1 Cape Observations, p. 98.

2 Transactions, Royal Dublin Society, vol. 2.

NEBULAS AND CLUSTERS 211

Dr. See found that these brown patches seem to
cluster in certain regions of the Milky Way.1

From a comparison of Trouvelot's drawing of
the small elongated nebula near the great nebula
in Andromeda with recent photographs, Mr. Easton
infers that this small nebula has probably rotated
through an angle of about 15° in 25 years. An
examination I have made of photographs taken
in different years seems to me to confirm this
suspicion, which, if true, is evidently a most
interesting phenomenon.

Dr. Max Wolf of Heidelberg finds, by spectrum
photography, that the well-known " ring nebula "
in Lyra consists of four rings composed of four
different gases. Calling the inner ring A, the
next B, the next C, and the outer D, he finds that
A is the smallest ring, and is composed of an un-
known gas ; the next largest, B, is composed
of hydrogen gas ; the next, C, consists of helium
gas ; and the outer and largest ring, D, is composed
— like A — of an unknown gas. As the molecular
weight of hydrogen is 2*016, and that of helium is
3'96, Prof. Bohuslav Brauner suggests that the
molecular weight of the gas composing the inner
ring A is smaller than that of hydrogen, and the
molecular weight of the gas forming the outer
ring D is greater than that of helium. He also
suggests that the gas of ring A may possibly be
identical with the " coronium " of the solar

1 Ast. Nach., 3628, quoted in The Observatory, April, 1900.

ASTRONOMICAL CURIOSITIES

corona, for which Mendelief found a hypothetical
atomic and molecular weight of 0'4.1

With reference to the nebular hypothesis of
Laplace, Dr. A. R. Wallace argues that " if there
exists a sun in a state of expansion in which our
sun was when it extended to the orbit of Neptune,
it would, even with a parallax of ^jth of a second,
show a disc of half a second, which could be seen
with the Lick telescope." My reply to this objec-
tion is, that with such an expansion there would
probably be very little " intrinsic brightness,"
and if luminous enough to be visible the spectrum
would be that of a gaseous nebula, and no known
star gives such a spectrum. But some planetary
nebulae look like small stars, and with high
powers on large telescopes would probably show
a disc. On these considerations, Dr. Wallace's
objection does not seem to be valid.

It is usually stated in popular works on
astronomy that the spectra of gaseous nebulae
show only three or four bright lines on a faint con-
tinuous background. But this is quite incorrect.
No less than forty bright lines have ..been seen
and measured in the spectra of gaseous nebulas.2
This includes 2 lines of " nebulium," 11 of
hydrogen, 5 of helium, 1 of oxygen (?), 3 of
nitrogen (?), 1 of silicon (?), and 17 of an unknown
substance. In the great nebulas in Orion 30
bright lines have been photographed.3

1 Nature, April 8, 1909.
2 Problems in Astrophysics, p. 477. 3 Ibid., p. 499.

NEBULAE AND CLUSTERS

D' Arrest found that " gaseous nebulas are rarely
met with outside the Milky Way, and never at a
considerable distance from it." l

Mr. A. E. Fath thinks that "no spiral nebula
investigated has a truly continuous spectrum."
He finds that so feeble is the intensity of the light
of the spiral nebulae that, while a spectrogram
of Arcturus can be secured with the Mills spectro-
graph " in less than two minutes," " an exposure
of about 500 hours would be required for the
great nebula in Andromeda, which is of the same
spectral type." 2 Mr. Fath thinks that in the case
of the Andromeda nebula, the " star cluster "
theory seems to be the only one that can at all
adequately explain the spectrum obtained." 3

Prof. Barnard finds that the great cluster in
Hercules (Messier 13) is " composed of stars of
different spectral types." This result was
confirmed by Mr. Fath.4

From observations with the great 40-inch
telescope of the Yerkes Observatory (U.S. A),
Prof. Barnard finds that the nucleus of the
planetary nebula H. iv. 18 in Andromeda is
variable to the extent of at least 3 magnitudes.
At its brightest it is about the 12th magnitude ;
and the period seems to be about 28 days.
Barnard says, " I think this is the first case in

1 Copernicus, vol. iii. p. 55.

2 Lick Observatory Bulletin, No. 149.

3 Ibid. 4 Ibid.

ASTRONOMICAL CURIOSITIES

which the nucleus of a planetary or other nebula
has been shown to be certainly variable." " The
normal condition seems to be faint — the nucleus
remaining bright for a few days only. In an
ordinary telescope it looks like a small round disc of
a bluish green colour." He estimated the bright-
ness of the nebula as that of a star of 8' 2 magni-
tude.1 Even in a telescope of 4 Inches aperture,
this would be a fairly bright object. It lies about
3£ degrees south-west of the star t Andromedse.

The so-called "globular clusters" usually
include stars of different brightness ; compara-
tively bright telescopic stars of the 10th to 13th
magnitude with faint stars of the 15th to 17th
magnitude. Prof. Perrine of the Lick Observatory
finds that (a) " the division of the stars in globular
clusters into groups, differing widely in bright-
ness, is characteristic of these objects " ; (6) " the
globular clusters are devoid of true nebulosity " ;
and (c) "stars fainter than 15th magnitude pre-
dominate in the Milky Way and globular clusters,
but elsewhere are relatively scarce." He found
that " exposures of one hour or thereabouts showed
as many stars as exposures four to six times as
long ; the only effect of the longer exposures being
in the matter of density." This last result con-
firms the late Dr. Roberts' conclusions. Perrine
finds that for clusters in the Milky Way, the faint
stars (15th to 17th magnitude) "are about as
1 Monthly Notice*, R.A.S., April, 1008, pp. 465-481.

NEBULA AND CLUSTERS 215

numerous in proportion to the bright stars (10th
to 13th magnitude) as in the globular clusters
themselves." This is, however, not the case with
globular clusters at a distance from the Milky Way.
In these latter clusters he found that "in the regions
outside the limits of the cluster there are usually
very few faint stars, hardly more than one-fourth
or one-tenth as many as there are bright stars " ;
and he thinks that " this paucity of faint stars "
in the vincity of these clusters " gives rise to the
suspicion that all regions at a distance from the
Galaxy may be almost devoid of these very faint
stars." The late Prof. Keeler's series of nebular
photographs " in or near the Milky Way " tend
to confirm the above conclusions. Perrine finds
the northernmost region of the Milky Way "to
be almost, if not entirely, devoid of globular
clusters." l

According to Sir John Herschel, " the sublimity
of the spectacle afforded " by Lord Rosse's great
telescope of 6 feet in diameter of some of the
" larger globular and other clusters " " is declared
by all who have witnessed it, to be such that no
words can express." 2

In his address to the British Association at
Leicester in 1907, Sir David Gill said —

"Evidence upon evidence has accumulated to
show that nebulae consist of the matter out of

1 Lick Observatory Bulletin, No. 155 (February, 1909).
- Outlines of Astronomy, par. 870 (Edition of 1875).

216 ASTRONOMICAL CURIOSITIES

which stars have been and are being evolved. . . .
The fact of such an evolution with the evidence
before us, can hardly be doubted. I most fully
believe that, when the modifications of terrestrial
spectra under sufficiently varied conditions of
temperature, pressure, and environment, have
been further studied, this connection will be
greatly strengthened."

CHAPTER XVIII

Historical

THE grouping of the stars into constellations
is of great antiquity. The exact date of
their formation is not exactly known, but
an approximate result may be arrived at from
the following considerations. On the celestial
spheres, or " globes," used by the ancient astro-
nomers, a portion of the southern heavens of
a roughly circular form surrounding the South
Pole was left blank. This space presumably con-
tained the stars in the southern hemisphere which
they could not see from their northern stations.
Now, the centre of this circular blank space most
probably coincided with the South Pole of the
heavens at the time when the constellations were
first formed. Owing to the "Precession of the
Equinoxes " this centre has now moved away
from the South Pole to a considerable distance.
It can be easily computed at what period this
centre coincided with the South Pole, and calcula-
tions show that this was the case about 2700 B.C.
The position of this circle also indicates that the

218 ASTRONOMICAL CURIOSITIES

constellations Avere formed at a place between 36°
and 40° north latitude, and therefore probably
somewhere in Asia Minor north of Mesopotamia.
Again, the most ancient observations refer to
Taurus as the equinoxial constellation. Virgil
says —

" Candidus auratis aperit cum cornibus annum
Taurus." l

This would indicate a date about 3000 B.C.
There is no tradition, however, that the constella-
tion Gemini was ever seen to occupy this position,
so that 3000 B.C. seems to be the earliest date
admissible.2

Prof. Sayce thinks that the "signs of the
Zodiac " had their origin in the plains of Mesopo-
tamia in the twentieth or twenty-third century
B.C., and Brown gives the probable date as 2084

B.C.3

According to Seneca, the study of astronomy
among the Greeks dates back to about 1400 B.C. ;
and the ancient constellations were already
classical in the time of Eudoxus in the fourth
century B.C. Eudoxus (408-355 B.C.) observed the
positions of forty-seven stars visible in Greece,
thus forming the most ancient star catalogue
which has been preserved. He was a son of

1 Georgics, i. 11. 217-18.

2 See paper by Mr. and Mrs. Maunder in Monthly Notices,
B.A.S., March, 1904, p. 506.

3 Primitive Constellations, vol. ii. p. 143.

HISTORICAL 219

Eschinus, and a pupil of Archytas and probably
Plato.

The work of Eudoxus was put into verse by the
poet Aratus (third century B.C.). This poem
describes all the old constellations now known,
except Libra, the Balance, which was at that time
included in the Claws of the Scorpion. About
B.C. 50, the Romans changed the Claws, or Chelae,
into Libra. Curious to say, Aratus states that the
constellation Lyra contained no bright star!1
Whereas its principal star, Vega, is now one of
the brightest stars in the heavens 1

With reference to the origin of the constellations,
Aratus says —

" Some men of yore

A nomenclature thought of and devised
And forms sufficient found."

This shows that even in the time of Aratus the
constellations were of great antiquity.
Brown says —

"Writers have often told us, speaking only
from the depths of their ignorance, how ' Chaldean '
shepherds were wont to gaze at the brilliant
nocturnal sky, and to imagine that such and such
stars resemble this or that figure. But all this
is merely the old effort to make capital out of
nescience, and the stars are before our eyes to
prove the contrary. Having already certain fixed
ideas and figures in his mind, the constellation-
former, when he came to his task, applied his

1 Hecherches $ur VHistoire de VAstronomie Ancienne, by Paul
Tannery (1893), p. 298.

220 ASTRONOMICAL CURIOSITIES

figures to the stars and the stars to his figures
as harmoniously as possible." * " Thus e.g. he
arranged the stars of Andromeda into the repre-
sentation of a chained lady, not because they
naturally reminded him (or anybody else) of such
a figure, but because he desired to express that
idea."

A coin of Manius Aquillus, B.C. 94, shows four
stars in Aquila, and seems to be the oldest repre-
sentation extant of a star group. On a coinrof
B.C. 43, Dr. Vencontre found five stars, one of which
was much larger than the others, and concludes
that it represents the Hyades (in Taurus). He
attributes the coin to P. Clodius Turrinus, who
probably used the constellation Taurus or Tauri-
nus as a phonetic reference to his surname. A coin
struck by L. Lucretius Trio in 74 B.C., shows the
seven stars of the Plough, or as the ancients called
them Septem Triones. Here we have an allusion
to the name of the magistrate Trio.2

In a work published in Berne in 1760, Schmidt
contends that the ancient Egyptians gave to the
constellations of the Zodiac the names of their
divinities, and expressed them by the signs which
were used in their hieroglyphics.3

Hesiod mentions Orion, the Pleiades, Sirius,
Aldebaran, and Arcturus ; and Homer refers to
Orion, Arcturus, the Pleiades, the Hyades, the

1 Primitive Constellation*, vol. ii. p. 225.

2 Nature, October 2, 1890.

8 Lalande's Astronomic, vol. i. pp. 243-4.

HISTORICAL

Great Bear (under the name of Amaxa, the
Chariot), and the tail of the Little Bear, or
" Cynosura."

Hipparchus called the constellations Asterisms
(doreptoTAos), Aristotle and Hyginus So/mra (bodies),
and Ptolemy ^xw*-™ (figures). By some they
were called , Mop^wo-cts (configurations), and by
others Merewpe. Proclus called those near the
ecliptic ZwSia (animals). Hence our modern name
Zodiac.

Hipparchus, Ptolemy, and Al-Sufi referred the
positions of the stars to the ecliptic. They are
now referred to the equator. Aboul Hassan in the
thirteenth century (1282) was the first to use Right
Ascensions and Declinations instead of Longitudes
and Latitudes. The ancient writers described the
stars by their positions in the ancient figures.
Thus they spoke of "the star in the head of
Hercules," "the bright star in the left foot of
Orion " (Rigel) ; but Bayer in 1603 introduced the
Greek letters to designate the brighter stars, and
these are now universally used by astronomers.
These letters being sometimes insufficient, Hevelius
added numbers, but the numbers in Flamsteed's
Catalogue are now generally used.

Ptolemy and all the ancient writers described
the constellation figures as they are seen 011
globes, that is from the outside. Bayer in his
Atlas, published in 1603, reversed the figures to
show them as they would be seen from the interior

222 ASTRONOMICAL CURIOSITIES

of a hollow globe and as, of course, they are seen
in the sky. Hevelius again reversed Bayer's
figures to make them correspond with those of
Ptolemy. According to Bayer's arrangement,
Betelgeuse (a Orionis) would be on the left
shoulder of Orion, instead of the right shoulder
according to Ptolemy and Al-Sufi, and Rigel
(ft Orionis) on the right foot (Bayer) instead of
the left foot (Ptolemy). This change of position
has led to some confusion; but at present the
positions of the stars are indicated by their Right
Ascensions and Declinations, without any reference
to their positions in the ancient figures.

The classical constellations of Hipparchus and
Ptolemy number forty-eight, and this is the
number described by Al-Sufi in his "Description
of the Fixed Stars " written in the tenth century

A.D.

Firminicus gives the names of several constella-
tions not mentioned by Ptolemy. M. Freret
thought that these were derived from the
Egyptian' sphere of Petosiris. Of these a Fox
was placed north of the Scorpion ; a constellation
called Cynocephalus near the southern constella-
tion of the Altar (Ara); and to the north of
Pisces was placed a Stag. But all these have long
since been discarded. Curious to say neither the
Dragon nor Cepheus appears on the old Egyptian
sphere.1

1 Lalande's Astronomic, vol. i. pp. 242-3.

HISTORICAL 223

Other small constellations have also been
formed by various astronomers from time to
time, but these have disappeared from our
modern star maps. The total number of con-
stellations now recognized in both hemispheres
amounts to eighty-four.

The first catalogue formed was nominally that
of Eudoxus in the fourth century B.C. (about 370
B.C.). But this can hardly be dignified by the
name of catalogue, as it contained only forty-
seven stars, and it omits several of the brighter
stars, notably Sirius ! The first complete (or nearly
complete) catalogue of stars visible to the naked
eye was that of Hipparchus about 129 B.C. Ptolemy
informs us that it was the sudden appearance of
a bright new or "temporary star" in the year
134 B.c. in the constellation Scorpio which led
Hipparchus to form his catalogue, and there
seems to be no reason to doubt the accuracy of
this statement, as the appearance of this star
is recorded in the Chinese Annals. The Cata-
logue of Hipparchus contains only 1080 stars ; but
as many more are visible to the naked eye,
Hipparchus must have omitted those which are
not immediately connected with the old constella-
tion figures of men and animals. ,

Hipparchus' Catalogue was revised by Ptolemy
in his famous work the Almagest. Ptolemy
reduced the positions of the stars given by
Hipparchus to the year 137 A.D. ; but used a

224 ASTRONOMICAL CURIOSITIES

wrong value of the precession which only corre-
sponded to about 50 A.D. ; and he probably
adopted the star magnitudes of Hipparchus with-
out any revision. Indeed, it seems somewhat
doubtful whether Ptolemy made any observations
of the brightness of the stars himself. Ptolemy's
catalogue contains 1022 stars.

Prof. De Morgan speaks of Ptolemy as "a
splendid mathematician and an indifferent
observer " ; and from my own examination of
Al-Sufi's work on the Fixed Stars, which was
based on Ptolemy's work, I think that De
Morgan's criticism is quite justified.

Al-Sufi's Description of the Fixed Stars was
written in the tenth century and contains 1018
stars. He seems to have adopted the positions
of the stars given by Ptolemy, merely correcting
them for the effects of precession ; but he made a
very careful revision of the star magnitudes of
Ptolemy (or Hipparchus) from his own observa-
tions, and this renders his work the most valu-
able, from this point of view, of all the ancient
catalogues.

Very little is known about Al-Sufi's life, and the
few details we have are chiefly derived from the
works of the historians Abu'-l-faradji and Casiri,
and the Oriental writers Hyde, Caussin, Sedillot,
etc. Al-Sufi's complete name was Abd-al-Rahman
Bin Umar Bin Muhammad Bin Sahl Abu'l-husain
al-Sufi al-Razi. The name Sufi indicates that he

HISTORICAL 225

belonged to the sect of Sufis (Dervishes), and the
name Razi that he lived in the town of Ra'i in
Persia, to the east of Teheran. He was born on
December 7, 903 A.D., and died on May 25, 986, so
that, like many other astronomers, he lived 'to a
good old age. According to ancient authorities,
Al-Sufi — as he is usually called — was a very
learned man, who lived at the courts of Schiraz
and Baghdad under Adhad-al-Davlat — of the
dynasty of the Buides — who was then the ruler
of Persia. Al-Sufi was held in high esteem and
great favour by this prince, who said of him,
" Abd-al-Rahman al-Sufi taught me to know the
names and positions of the fixed stars, Scharif
Ibn al-Aalam the use of astronomical tables, and
Abu Ali al-Farisi instructed me in the principles
of grammar." Prince Adhad-al-Davlat died on
March 26, 983. According to Caussin, Al-Sufi
also wrote a book 011 astrology, and a work
entitled Al-Ardjouze, which seems to have been
written in verse, but its subject is unknown. He
also seems to have determined the exact length
of the year, and to have undertaken geodetic
measurements. The al-Aalam mentioned above
was also an able astronomer, and in addition to
numerous observations made at Baghdad, he
determined with great care the precession of the
equinoxes. He found the annual constant of
precession to be 51"'4, a value which differs but
little from modern results.

226 ASTRONOMICAL CURIOSITIES

In the year 1874, the late M. Schjellerup, the
eminent Danish astronomer, published a French
translation of two Arabic manuscripts written by
Al-Sufi and entitled " A Description of the Fixed
Stars." One of these manuscripts is preserved in
the Royal Library at Copenhagen, and the other
in the Imperial Library at St. Petersburgh.1

Al-Sufi seems to have been a most careful and
accurate observer, and although, as a rule, his
estimates of the relative brightness of stars are in
fairly good agreement with modern estimates and
photometric measures, there are many remarkable
and interesting differences. Al-Sufi's observations
have an important bearing on the supposed
" secular variation " of the stars ; that is, the slow
variation in light which may have occurred in the
course of ages in certain stars, apart from the
periodical variation which is known to occur in
the so-called variable stars. More than 900 years
have now elapsed since the date of Al-Sufi's
observations (about A.D. 964) and over 2000 years
in the case of Hipparchus, and although these
periods are of course very short in the life-history
of any star, still some changes may possibly have
taken place in the brightness of some of them.

1 There are three copies of Al-Sufi's work in the Imperial
Library at Paris, but these are inaccurate. There is also one in
the British Museum Library, and another in the India Office
Library ; but these are imperfect, considerable portions of the
original work being missing.

HISTORICAL

There are several cases in which a star seems to
have diminished in light since Al-Sufi's time.
This change seems to have certainly occurred in
the case of 0 Eridani, ft Leonis, £ Piscis Australis,
and some others. On the other hand, some stars
seem to have certainly increased in brightness,
and the bearing of these changes on the question
of " stellar evolution " will be obvious.

In most cases Al-Sufi merely mentions the
magnitude which he estimated a star to be ; such
as "third magnitude," "fourth," "small third
magnitude," "large fourth," etc. In some cases,
however, he directly states that a certain star is
a little brighter than another star near it. Such
cases — unfortunately not numerous — are very
valuable for comparison with modern estimates
and measures, when variation is suspected in the
light of a star. The estimates of Argelander,
Heis, and Houzeau are based on the same scale as
that used by Ptolemy and Al-Sufi. Al-Sufi's
estimates are given in thirds of a magnitude.
Thus, " small third magnitude " means 3|, or 3*33
magnitude in modern measures ; " large fourth,"
3| or 3' 66 magnitude. These correspond with the
estimates of magnitude given by Argelander,
Heis, and Houzeau in their catalogues of stars
visible to the naked eye, and so the estimates can
be directly compared.

I have made an independent identification of
all the stars mentioned by Al-Sufi. In the

228 ASTRONOMICAL CURIOSITIES

majority of cases my identifications concur with
those of Schjellerup ; but in some cases I cannot
agree with him. In a few cases I have found
that Al-Sufi himself, although accurately describ-
ing the position of the stars observed by him,
has apparently misidentified the star observed by
Hipparchus and Ptolemy. This becomes evident
when we plot Ptolemy's positions (as given by
Al-Sufi) and compare them with Al-Sufi' s descrip-
tions of the stars observed by him. This I have
done in all cases where there seemed to be any
doubt ; and in this way I have arrived at some
interesting results which have escaped the notice
of Schjellerup. This examination shows clearly,
I think, that Al-Sufi did not himself measure the
positions of the stars he observed, but merely
adopted those of Ptolemy, corrected for the effect
of precession. The great value of his work, how-
ever, consists in his estimates of star magnitudes,
which seem to have been most carefully made,
and from this point of view, his work is in-
valuable. Prof. Pierce says, "The work which
the learning of M. Schjellerup has brought to
light is so important that the smallest errors of
detail become interesting." 1

Although Al-Sufi' s work is mentioned by the

writers referred to above, no complete translation

of his manuscript was made until the task was

undertaken by Schjellerup, and even now Al-Sufi's

1 Harvard Annals, vol. ix. p. 51.

HISTORICAL 229

name is not mentioned in some popular works on
astronomy ! But lie was certainly the best of all
the old observers, and his work is deserving of
the most careful consideration.

Al-Sufi's descriptions of the stars were, it is
true, based on Ptolemy's catalogue, but his work
is not a mere translation of that of his pre-
decessor. It is, on the contrary, a careful and
independent survey of the heavens, made from
his own personal observations, each of Ptolemy's
stars having been carefully examined as to its
position and magnitude, and Ptolemy's mis-
takes corrected. In examining his descriptions,
Schjellerup says, "We soon see the vast extent
of his labours, his perseverance, and the minute
accuracy and almost modern criticism with which
he executed his work." In fact, Al-Sufi has given
us a careful description of the starry sky as it
appeared in his time, and one which deserves the
greatest confidence. It far surpasses the work
of Ptolemy, which had been without a rival for
eight centuries previously, and it has only been
equalled in modern times by the surveys of
Argelander, Gould, Heis, and Houzeau. Plato
remarked with reference to the catalogue of
Hipparchus, Ccelam posteris in hereditatem re-
lictum, and the same may be said of Al-Sufi's
work. In addition to his own estimates of star
magnitudes, Al-Sufi adds the magnitudes given
by Ptolemy whenever Ptolemy's estimate differs

230 ASTRONOMICAL CURIOSITIES

from his own ; and this makes his work still more
valuable, as Ptolemy's magnitudes given in all the
editions of the Almagest now extant are quite
untrustworthy.

In the preface to his translation of Al-Sufi's
work, Schjellerup mentions some remarkable dis-
crepancies between the magnitudes assigned to
certain stars by Ptolemy and Argelaiider. This
comparison is worthy of confidence as it is
known that both Al-Sufi and Argelander adopted
Ptolemy's (or Hipparchus') scale of magnitudes.
For example, all these observers agree that /? Ursse
Minoris (Ptolemy's No. 6 of that constella-
tion) is of the 2nd magnitude, while in the case
of y Ursse Minoris (Ptolemy's No. 7), Ptolemy
called it 2nd, and Argelander rated it 3rd ;
Argelander thus making y one magnitude fainter
than Ptolemy's estimate. Now, Al-Sufi, observing
over 900 years ago, rated y of the 3rd magni-
tude, thus correcting Ptolemy and agreeing with
Argelander. Modern photometric measures con-
firm the estimates of Al-Sufi and Argelander.
But it is, of course, possible that one or both
stars may be variable in light, and /? has actually
been suspected of variation. Almost all the
constellations afford examples of this sort. In
the majority of cases, however, Al-Sufi agrees
well with Argelander and Heis, but there are in
some cases differences which suggest a change
in relative brightness.

HISTORICAL

Among other remarkable things contained in
Al-Sufi's most interesting work may be mentioned
the great nebula in Andromeda, which was first
noticed in Europe as visible to the naked eye by
Simon Marius in 1612. Al-Sufi, however, speaks
of it as a familiar object in his time.

Schjellerup says —

" For a long time many of the stars in Ptolemy's
catalogue could not be identified in the sky.
Most of these discordances were certainly due to
mistakes in copying, either in longitude or lati-
tude. Many of these differences were, however,
corrected by the help of new manuscripts. For
this purpose Al-Sufi's work is of great importance.
By a direct examination of the sky he succeeded
in finding nearly all the stars reported by
Ptolemy (or Hipparchus). And even if his
criticism may sometimes seem inconclusive, his
descriptions are not subject to similar defects,
his positions not depending solely on the places
given in Ptolemy's catalogue. For, in addition to
the longitudes and latitudes quoted from Ptolemy,
he has described by alignment the positions of
the stars referred to. In going from the brightest
and best known stars of each constellation he
indicates the others either by describing some
peculiarity in their position, or by giving their
mutual distance as so many cubits (dzird), or a
span (schibr), units of length which were used at
that time to measure apparent celestial distances.
The term dzird means literally the fore-arm from
the bone of the elbow to the tip of the middle
finger, or an ell. We should not, however, con-
clude from this that the Arabians were so un-
scientific as to measure celestial distances by an
ell, as this would be quite in contradiction to

232 ASTRONOMICAL CURIOSITIES

their well-known knowledge of Geometry and
Trigonometry."

With reference to the arc or angular distance
indicated by the "cubit," Al-Sufi states in his
description of the constellation Auriga that the
dzird (or cubit) is equal to 2° 20'. Three cubits,
therefore, represent 7°, and 4 cubits 9° 20'.

In Al-Sufi's own preface to his work, after
first giving glory to God and blessings on "his
elected messenger Muhammed and his family,"
he proceeds to state that he had often "met
with many persons who wished to know the fixed
stars, their positions on the celestial vault, and
the constellations, and had found that these
persons may be divided into two classes. One
followed the method of astronomers and trust
to spheres designed by artists, who not knowing,
the stars themselves, take only the longitudes
and latitudes which they find in the books, and
thus place the stars on the sphere, without being
able to distinguish truth from error. It then
follows that those who really know the stars in
the sky find on examining these spheres that
many stars are otherwise than they are in the
sky. Among these are Al-Battani, Atarid and
others."

Al-Sufi seems rather hard on Al-Battani (or
Albategnius as he is usually called) for he is
generally considered to have been the most

HISTORICAL 233

distinguished of the Arabian astronomers. His
real name was Mohammed Ibn Jaber Ibn Senaii
Abu Abdallah Al-Harrani. He was born about
A.D. 850 at Battan, near Harran in Mesopotamia,
and died about A.D. 929. He was the first to
make use of sines instead of chords, and versed
sines. The ALphonsine Tables of the moon's
motions were based on his observations.

After some severe criticisms on the work of
Al-Battani and Atarid, Al-Sufi goes on to say
that the other class of amateurs who desire to
know the fixed stars follow the method of the
Arabians in the science of Anva1 and the
mansions of the moon and the books written on
this subject. Al-Sufi found many books on the
anva, the best being those of Abu Hanifa al-
Dinavari, This work shows that the author
knew the Arabic tradition better than any of
the other writers on the subject. Al-Sufi, how-
ever, doubts that he had a good knowledge of
the stars themselves, for if he had he would not
have followed the errors of his predecessors.

According to Al-Sufi, those who know one of
these methods do not know the other. Among
these is Abu-Hanifa, who states in his book that
the names of the twelve signs (of the Zodiac)
did not originate from the arrangement or

1 The science of the risings and settings of the stars was called
Urn el-anwa (Caussin, Notices et Extraits des Manuscrits de la
Bibliotheque due Hoi, tome xii. p. 237).

ASTRONOMICAL CURIOSITIES

configuration of the stars resembling the figure
from which the name is derived. The stars, Abu-
Hanifa said, "change their places, and although
the names of the signs do not change, yet the
arrangement of the stars ceases to be the same.
This shows that he was not aware of the fact
that the arrangement of the stars does not
change, and their mutual distances and their
latitudes, north and south of the ecliptic, are
neither increased nor diminished." "The stars,"
Al-Sufi says, "do not change with regard to
their configurations, because they are carried
along together by a physical motion and by a
motion round the poles of the ecliptic. This is
why they are called fixed. Abu-Hanifa supposed
that they are termed fixed because their motion is
very slow in comparison with that of the planets."
"These facts," he says, "can only be known to
those who follow the method of the astronomers
and are skilled in mathematics."

Al-Sufi says that the stars of the Zodiac have
a certain movement following the order of the
signs, which according to Ptolemy and his
predecessors is a degree in 100 years. But accord-
ing to the authors of al-mumtahan and those
who have observed subsequently to Ptolemy,
it is a degree in 66 years. According to modern
measures, the precession is about 50"*35 per
annum, or one degree in 71J years.

Al-Siifi says that the Arabians did not make

HISTORICAL 235

use of the figures of the Zodiac in their proper
signification, because they divided the circum-
ference of the sky by the number of days
which the moon took to describe it — about 28
days — and they looked for conspicuous stars at
intervals which, to the eye, the moon appeared
to describe in a day and a night. They began
with al-scharatain, " the two marks " (a and
/3 Arietis) which were the first striking points
following the point of the spring equinox. They
then sought behind these two marks another
point at a distance from them, equal to the space
described by the moon in a day and a night.
In this way they found al-butatn (e, 3, and
p Arietis) ; after that al-tsuraija, the Pleiades ;
then al-dabaran, the Hyades, and thus all the
" mansions " of the moon. They paid no atten-
tion to the signs of the Zodiac, nor to the extent
of the figures which composed them. This is
why they reckoned among the "mansions" al-
Jiaka (A Orionis) which forms no part of the signs
of the Zodiac, since it belongs to the southern
constellation of the Giant (Orion). And similarly
for other stars near the Zodiac, of which Al-
Sufi gives some details. He says that Begulus
(a Leonis) was called by the Arabians al-maliki,
the Royal Star, and that al-anva consists of
five stars situated in the two wings of the Virgin.
These stars seem to be /?, 17, y, 8, and c Virginis,
which form with Spica (a Virginis) a Y-shaped

236 ASTRONOMICAL CURIOSITIES

figure. Spica was called simak al-azal, the un-
armed simak ; the " armed simak " being Arcturus,
simak al-ramih. These old Arabic names seem
very fanciful.

Al-Sufi relates that in the year 337 of the
Hegira (about A.D. 948) he went to Ispahan with
Prince Abul-fadhl, who introduced him to an
inhabitant of that city, named Varvadjah, well
known in that country, and famous for his
astronomical acquirements. Al-Sufi asked him
the names of the stars on an astrolabe which he
had, and he named Aldebaran, the two bright
stars in the Twins (Castor and Pollux), Regulus,
Sirius, and Procyon, the two Simaks, etc. Al-Sufi
also asked him in what part of the sky Al-fard
(a Hydrse) was, but he did not know ! After-
wards, in the year 349, this same man was at
the court of Prince Adhad-al-Davlat, and in the
presence of the Prince, Al-Sufi asked him the
name of a bright star — it was al-nasr al-vaki,
the falling Vulture (Vega), and he replied, " That
is al-aijuk " (Capella) ! thus showing that he
only knew the names of the stars, but did not
know them when he saw them in the sky.
Al-Sufi adds that all the women "who spin in
their houses" knew this star (Vega) by the
name of al-atsafi, the Tripod. But this could
not be said even of "educated women" at the
present day.

With reference to the number of stars which

HISTORICAL 237

can be seen with the naked eye, Al-Sufi says,
" Many people believe that the total number of
fixed stars is 1025, but this is an evident error.
The ancients only observed this number of stars,
which they divided into six classes according to
magnitude. They placed the brightest in the
1st magnitude ; those which are a little smaller
in the 2nd ; those which are a little smaller again
in the 3rd ; and so on to the 6th. As to those
which are below the 6th magnitude, they found
that their number was too great to count ; and
this is why they have omitted them. It is easy
to convince one's self of this. If we attentively fix
ourgaze on a constellation of which the stars are
well known and registered, we find in the spaces
between them many other stars which have
not been counted. Take, for example, the Hen
[Cygnus] ; it is composed of seventeen internal
stars, the first on the beak, the brightest on the tail,
the others on the wings, the neck and the breast ;
and below the left wing are two stars which do
not come into the figure. Between these different
stars, if you examine with attention, you will
perceive a multitude of stars, so small and so
crowded that we cannot determine their number.
It is the same with all the other constellations."
These remarks are so correct that they might
have been written by a modern astronomer. It
should be added, however, that all the faint
stars referred to by Al-Sufi — and thousands of

238 ASTRONOMICAL CURIOSITIES

others still fainter — have now been mapped down
and their positions accurately determined.

About the year 1437, Ulugh Beigh, son of Shah
Rokh, and grandson of the Mogul Emperor
Tamerlane, published a catalogue of stars in
which he corrected Ptolemy's positions. But he
seems to have accepted Al-Sufi's star magnitudes
without any attempt at revision. This is unfortu-
nate, for an independent estimate of star magni-
tudes made in the fifteenth century would now
be very valuable for comparison with Al-Sufi's
work and with modern measures. Ulugh Beigh's
catalogue contains 1018 stars, nearly the same
number as given by Ali-Sufi.1

1 See Mr. E. B. Knobel'a papers on tliia subject in the Monthly
Notices, R.A.S., for 1879 and 1884.

CHAPTER XIX

The Constellations1

CURIOUS to say, Al-Sufi rated tke Pole Star
as 3rd magnitude ; for it is now only
slightly less than the 2nd. At present
it is about the same brightness as ft of the same
constellation (Ursa Minor) which Al-Sufi rated
2nd magnitude. It was, however, also rated 3rd
magnitude by Ptolemy (or Hipparchus), and it
may possibly have varied in brightness since
ancient times. Admiral Smyth says that in his
time (1830) it was " not even a very bright third
size " (!) 2 Spectroscopic measures show that it is
approaching the earth at the rate of 16 miles a
second ; but this would have no perceptible effect
on its brightness in historical times. This may
seem difficult to understand, and to some perhaps

1 In reading this chapter the reader is recommended to have a
Star Atlas beside him for reference ; Proctor's smaller Star Atlas
will be found very convenient for this purpose. On the title-page
of this useful work the author quotes Carlyle's words, "Why
did not somebody teach me the constellations and make me at
home in the starry heavens which are always overhead, and
which I don't half know to this day ? "

- Bedford Catalogue, p. 29.

240 ASTRONOMICAL CURIOSITIES

incredible ; but the simple explanation is that its
distance from the earth is so great that a journey
of even 2000 years with the above velocity would
make no appreciable difference in its distance !
This is undoubtedly true, as a simple calculation
will show, and the fact will give some idea of the
vast distance of the stars. The well-known 9th
magnitude companion to the Pole Star was seen
by day in the Dorpat telescope by Struve and
Wrangel ; and " on one occasion by Encke and
Argelander." x

The star /? Ursse Minoris was called by the
Arabians Kaiikab al-shamdli, the North Star, as
it was — owing to the precession of the Equinoxes
— nearer to the Pole in ancient times than our
present Pole Star was then.

The " Plough " (or Great Bear) is supposed to
represent a waggon and horses. " Charles' Wain "
is a corruption of "churl's wain," or peasant's
cart. The Arabians thought that the four stars
in the quadrilateral represented a bier, and the
three in the " tail " the children of the deceased
following as mourners ! In the Greek mythology,
Ursa Major represented the nymph Callisto, a
daughter of Lycaon, who was loved by Jupiter,
and turned into a bear by the jealous Juno. Among
the old Hindoos the seven stars represented the
seven Rishis. It is the Otawa of the great
Finnish epic, the " Kalevala." It was also called
1 Cosmos, vol. iii. p. 87.

THE CONSTELLATIONS 241

" David's Chariot," and in America it is known as
"The Dipper."

Closely north of the star 6 in Ursa Major is a
small star known as Flamsteed 26. This is not
mentioned by Al-Sufi. but is now, I find from
personal observation, very visible, and indeed
conspicuous, to the naked eye. I find, however,
that owing to the large " proper motion " of the
bright star (1"*1 per annum) the two stars were
much closer together in Al-Sufi's time than they
are at present, and this probably accounts for
Al-Sufi's omission. This is an interesting and
curious fact, and shows the small changes which
occur in the heavens during the course of
ages.

Close to the star £, the middle star of the " tail "
of Ursa Major (or handle of the " Plough "), is a
small star known as Alcor, which is easily visible
to good eyesight without optical aid. It is
mentioned by Al-Sufi, who says the Arabians
called it al-suha, " the little unnoticed one." He
says that " Ptolemy does not mention it, and it
is a star which seems to test the powers of
the eyesight." He adds, however, an Arabian
proverb, " I show him al-suha, and he shows me
the moon," which seems to suggest that to some
eyes, at least, it was no test of sight at all. It
has, however, been suspected of variation in light.
It was rated 5th magnitude by Argelander, Heis,
and Houzeau, but was measured 4*02 at Harvard

242 ASTRONOMICAL CURIOSITIES

Observatory. It has recently been found to be
a spectroscopic binary.

The constellation of the Dragon (Draco) is prob-
ably referred to in Job (chap. xxvi. v. 13), where
it is called " the crooked serpent." In the Greek
mythology it is supposed to represent the dragon
which guarded the golden apples in the Garden
of the Hesperides. Some have suggested that it
represented the serpent which tempted Eve.
Dryden says, in his translation of Virgil —

" Around our Pole the spiry Dragon glides,
And like a wand'ring stream the Bears divides."

The fact that the constellation Bootis rises
quickly and sets slowly, owing to its lying
horizontally when rising and vertically when
setting, was noted by Aratus, who says —

" The Bearward now, past seen,
But more obscured, near the horizon lies ;
For with the four Signs the Ploughman, as he sinks,
The deep receives ; and when tired of day
At even lingers more than half the night,
When with the sinking sun he likewise sets
These nights from bis late setting bear their name." l

The cosmical setting of Bootis — that is, when he
sets at sunset — is stated by Ovid to occur on
March 5 of each year.

With reference to the constellation Hercules,
Admiral Smyth says —

" The kneeling posture has given rise to

1 Heavenly Display, 579-85,

THE CONSTELLATIONS 243

momentous discussion ; and whether it represents
Lycaoii lamenting his daughter's transformation,
or Prometheus sentenced, or Ixion ditto, or
Thamyrus mourning his broken fiddle, remains
still uncertain. But in process of time, this figure
became a lion, and Hyginus mentions both the
lion's skin and the club ; while the right foot's
being just over the head of the Dragon, satisfied
the my thologists that he was crushing the Lernsean
hydra. . . . Some have considered the emblem as
typifying the serpent which infested the vicinity
of Cape Tsenarus, whence a sub-genus of Ophi-
dians still derives its name. At all events a poet,
indignant at the heathen exaltation of Hevelius,
has said —

" « To Cerberus, too, a place is given—
His home of old was far from heaven.' " l

Aratus speaks of Hercules as " the Phantom
whose name none can tell."

There were several heroes of the name of
Hercules, but the most famous was Hercules the
Theban, son of Jupiter and Alcmene wife of
Amphitryon, King of Thebes, who is said to have
lived some years before the siege of Troy, and
went 011 the voyage of the Argonauts about
1300 B.C. According to some ancient writers,
another Hercules lived about 2400 B.C., and was a
contemporary of Atlas and Theseus. But accord-
ing to Petau, Atlas lived about 1638 B.C., and
Lalande thought that this chronology is the more
probable.

The small constellation Lyra, which contains
1 Bedford Catalogue, p. 385.

244 ASTRONOMICAL CURIOSITIES

the bright star Vega, is called by Al-Sufi the
Lyre, the Goose, the Persian harp, and the Tor-
toise. In his translation of Al-Sufi's work,
Schjellerup suggests that the name " Goose " may
perhaps mean a plucked goose, which somewhat
resembles a Greek lyre, and also a tortoise. The
name of the bright star Vega is a corruption of
the Arabic vdki. Ptolemy and Al-Sufi included
all the very brightest stars in the " first magni-
tude," making no distinction between them, but
it is evident at a glance that several of them,
such as Arcturus and Vega, are brighter than an
average star of the first magnitude, like Aldebaran.
The constellation Perseus, which lies south-east
of " Cassiopeia's Chair," may be recognized by the
festoon formed by some of its stars, the bright
star a Persei being among them. It is called by
Al-Sufi " barschdnsch, Ilepo-evs, Perseus, who is
hamil rds al-gul, the Bearer of the head of al-gul'
According to Kazimirski, " Gul was a kind of demon
or ogre who bewilders travellers and devours them,
beginning at the feet. In general any mischievous
demon capable of taking all sorts of forms." In
the Greek mythology Perseus was supposed to be
the son of Jupiter and Danse. He is said to have
been cast into the sea with his mother and saved
by King Polydectus. He afterwards cut off the
head of Medusa, one of the Gorgons, while she
slept, and armed with this he delivered Andromeda
from the sea-monster.

THE CONSTELLATIONS 245

The constellation Auriga lies east of Perseus
and contains the bright star Capella, one of the
three brightest stars in the northern hemisphere
(the others being Arcturus and Vega). Theon, in
his commentary on Aratus, says that Bellerophon
invented the chariot, and that it is represented
in the heavens by Auriga, the celestial coachman.
According to Dupuis, Auriga represents Phaeton,
who tried to drive the chariot of the sun, and
losing his head fell into the river Eridanus. The
setting of Eridanus precedes by a few minutes
that of Auriga, which was called by some of the
ancient writers Amnis Phai-tontis.1 Auriga is
called by Al-Sufi numsick al-ainna — He who
holds the reins, the Coachman ; also al-indz, the
She-goat. M. Dorn found in Ptolemy's work, the
Greek name 'Hw'oxoi, Auriga, written in Arabic
characters. Al-Sufi says, "This constellation is
represented by the figure of a standing man
behind 'He who holds the head of al-gtiV
[Perseus], and between the Pleiades and the Great
Bear."

Capella is, Al-Sufi says, " the bright and great
star of the first magnitude which is on the left
shoulder [of the ancient figure] on the eastern edge
of the Milky Way. It is that which is marked
on the astrolabe as alaijilk" The real meaning
of this name is unknown. Schjellerup thought,
contrary to what Ideler says, that the name is
1 Lalande's Astronomic, vol. iv. p. 529.

246 ASTRONOMICAL CURIOSITIES

identical with the Greek word 'A'i£ (a goat).
Capella was observed at Babylon about 2000 B.C.,
and was then known as Dilgan. The Assyrian
name was Icu, and the Persian name colca. It
was also called Capra Hircus, Cabrilla, Amalthea,
and Olenia. In ancient times the rising of
Capella was supposed to presage the approach of
storms. Ovid says, " Olenia sidus pluviale Capellse."
The constellation Aquila is called by Al-Sufi
al-ukdb, the Eagle, or al-nasr al-td'ir, the flying
vulture. According to the ancient poets the
eagle carried nectar to Jupiter when he was
hidden in a cave in Crete. This eagle also assisted
Jupiter in his victory over the Giants and con-
tributed to his other pleasures. For these reasons
the eagle was consecrated to Jupiter, and was
placed in the sky. Al-Sufi says, " There are in this
figure three famous stars [y, a, and /? Aquilae],
which are called al-nasr al-tdir." Hence is derived
the modern name Altair for the bright star
a Aquilse. Al-Sufi says that the " common
people " call " the three famous stars " al-miz&n,
the Balance, 011 account of the equality of the
stars." This probably refers to the approximately
equal distances between y and a, and a and /?,
and not to their relative brightness. He says
"Between the bright one of the tail [£ Aquilse
and the star in the beak of the Hen [ft Cygni]
in the thinnest part of the Milky Way, we see
the figure of a little earthen jar, of which the

THE CONSTELLATIONS 247

stars begin at the bright one in the tail, and
extend towards the north-west. [This seems to
refer to e Aquilse and the small stars near it.]
They then turn towards the east in the base of
the jar, and then towards the south-east to a
little cloud [4, 5, etc. Vulpeculse, a well-known
group of small stars] which is found to the north
of the two stars in the shaft of the Arrow [a and

• l"

5 II

AL-SDFI'S "EARTHEN JAB."

/? Sagittae]. The cloud is on the eastern edge
of the jar, and the bright one 011 the tail on
the western edge ; the orifice is turned towards the
flying Vulture [Aquila], and the base toAvards the
north. Among these are distinguished some of
the fourth, fifth, and sixth magnitudes [includ-
ing, probably, 110, 111, 112, 113 Hercules, and
1 Vulpeculse] and Ptolemy says nothing of this
figure, except the bright star in the tail of the

248 ASTRONOMICAL CURIOSITIES

Eagle " (see figure). The above is a good example
of the minute accuracy of detail in Al-Sufi's
description.

The southern portion of Aquila was formerly
called Antinous, who was said to have been a
young man of great beauty born at Claudiopolis
in Bithynia, and drowned in the Nile. Others
say that he sacrificed his life to save that of the
Emperor Hadrian, who afterwards raised altars
in his honour and placed his image on coins.1

The constellation Pegasus, Al-Sufi says, "is
represented by the figure of a horse, which has the
head, legs, and forepart of the body to the end
of the back, but it has neither hind quarters nor
hind legs." According to Brown, Pegasus was the
horse of Poseidon, the sea god. Half of it was
supposed to be hidden in the sea, into which the
river Eridanus flowed.2 In the Greek mythology
it was supposed to represent the winged horse
produced by the blood which fell from the head
of Medusa when she was killed by Perseus !
Some think that it represents Bellerophoii's horse,
and others the horse of Mmrod. It was also
called Sagmaria and Ephippiatus, and was some-
times represented with a saddle instead of wings.

In describing the constellation Andromeda, Al-
Sufi speaks of two series of stars which start
from the great nebula in Andromeda ; one series

1 Lalande's Astronomic, vol. i. pp. 2G8-9.

2 Primitive Constellations, vol. i. p. 48.

THE CONSTELLATIONS

249

going through 32 Andromedse, *•, 8, and e to £
and T] ; and the other through v, /*, ft Andromedse
into the constellation Pisces. He says they
enclose a fish-shaped figure called by the Arabians
al-htit, the Fish, par excellence. He speaks of
two other series of stars which begin at r and v ,

.y.

+* \v

•x V--

AL-SUFI'S "PISHES" IN ANDROMEDA.

and diverging meet again at x Persei, forming
another "fish-like figure." The eastern stream
starts from r and passes through 55, y, 60, C2, 04,
and 65 Andromedae ; and the western stream
from v through x» 51, 54, and g Persei up to

250 ASTRONOMICAL CURIOSITIES

X Persei. The head of the first " fish," al-lnM, is
turned towards the north, and that of the second
towards the south (see figure).

Al-Sufi says that the stars a Persei, y, /?, 8, and
a Andromedae, and /3 Pegasi form a curved line.
This is quite correct, and this fine curve of bright
stars may be seen at a glance on a clear night
in September, when all the stars are high in
the sky.

The first constellation of the Zodiac, Aries, the
Ram, was called, according to Aratus and Eratos-
thenes, Kpibs. It is mentioned by Ovid under the
name of Hellas. It4was also called by the ancients
the Ram with the golden horns. Manilius
(fourth century B.C.) called it " The Prince." It is
supposed to have represented the god Bel.
Among the Accadians the sign meant " He who
dwells on the altar of uprightness." It first
appears on the Egyptian Zodiac; and it was
sacred to Jupiter Ammon. In the Greek
mythology it was supposed to represent the
ram, the loss of whose fleece led to the voyage
of the Argonauts. In the time of Hipparchus,
about 2000 years ago, it was the first sign of
the Zodiac, or that in which the sun is situated
at the Vernal Equinox (about March 21 in each
year). But owing to the precession of the
equinoxes, this point has now moved back into
Pisces.

The brightest star of Aries (a) is sometimes

THE CONSTELLATIONS 251

called Hamal, derived from the Arabic al-hamal,
a name given to the constellation itself by *A1-
Sufi. In the Accadian language it was called
Dilkur, " the dawn proclaimer." Ali-Sufi says
that close to a, " as if it were attached to it," is
a small star of the 6th magnitude, not mentioned
by Ptolemy. This is clearly K Arietis. The fact
of Al-Sufi having seen and noticed this small
star, which modern measures show to be below
the 5th magnitude, is good evidence of his keen
eyesight and accuracy of observation.

According to Al-Sufi, the stars ft and y Arietis
were called by the Arabians al-scharatain, "the
two marks." They marked the "first mansion
of the moon," and c, S, and p the second mansion.
With reference to these so-called "mansions of
the moon," Admiral Smyth says —

"The famous Manazil al-kamar, i.e. Lunar
mansions, constituted a supposed broad circle in
Oriental astronomy divided into twenty-eight
unequal parts, corresponding with .the moon's
course, and therefore called the abodes of the
moon. This was not a bad arrangement for a
certain class of gazers, since the luminary was
observed to be in or near one or other of these
parts, or constellations every night. Though
tampered with by astrologers, these Lunar
mansions are probably the earliest step in
ancient astronomy." x

Taurus, the second constellation of the Zodiac,

1 Bedford Catalogue, pp. 27, 28.

ASTRONOMICAL CURIOSITIES

was in ancient times represented by the figure
of a bull, the hinder part of which is turned
towards the south-west, and the fore part towards
the east. It had no hind legs, and the head was
turned to one side, with the horns extended
towards the east. Its most ancient name was
Te, possibly a corruption of the Accadiaii
dimmena, " a foundation - stone." The Greek
name is aOwp (0wwp, Eusebius). In the old
Egyptian mythology Taurus represented the
god Apis. According to Dupuis it#lso represented
the 10th " labour of Hercules," namely, his victory
over the cows of Geryon, King of Spain.1 It
was also supposed to represent the bull under
the form of which Jupiter carried off Europa,
daughter of Agenor, King of the Phoenicians. It
may also refer to lo or Isis, who is supposed
to have taught the ancient Egyptians the art
of agriculture.

Aldebaraii is the well-known bright red star
in the Hyades. It was called by Ptolemy Fulgur
succularum. Ali-Sufi says it was marked on the
old astrolabes as al-dabaran, " the Follower "
(because it follows the Hyades in the diurnal
motion), and also ain al-tsaur, the eye of the
bull. It may be considered as a standard star
of the 1st magnitude. Modern observations show
that it has a parallax of 0"'107. It is receding
from the earth, according to Vogel, at the rate
1 Lalande's Astronomie, vol. iv. p. 492.

THE CONSTELLATIONS 253

of about 30 miles a second ; but even with this
high velocity it will take thousands of years
before its brightness is perceptibly diminished.
It has a faint companion of about the 10th
magnitude at the distance of 118", which forms
a good " light test " for telescopes of 3 or 4 inches
aperture. I saw it well with a 4-inch Wray
in the Punjab sky. The Hyades were called
Succulce by the Romans, and in the Greek
mythology were said to be children of Atlas.

The star ft Tauri, sometimes called Nath, from
the Arabic al-ndtih, the butting, is a bright star
between Capella and y Orionis (Bellatrix). It is
on the tip of the horn in the ancient figure of
Taurus, and " therefore " (says Admiral Smyth)
" at the greatest distance from the hoof ; can this
have given rise to the otherwise pointless sarcasm
of not knowing B from a bull's foot ? "l Al-Sufi
says that an imaginary line drawn from the star
now known as A Tauri to r Tauri would pass
between v and K Tauri, which is quite correct,
another proof of the accuracy of his observations.
He also says that the star o> Tauri is exactly
midway between A and c, which is again correct.
He points out that Ptolemy's position of w is
incorrect. This is often the case with Ptolemy's
positions, and tends to show that Ptolemy adopted
the position given by Hipparchus without
attempting to verify their position in the sky.
1 Bedford Catalogue, p. 120.

254 ASTRONOMICAL CURIOSITIES

Al-Sufi himself adopts the longtitudes and
latitudes of the stars as given by Ptolemy in
the Almagest, but corrects the positions in his
descriptions, when he found Ptolemy's places
erroneous.

The famous group of the Pleiades is well known ;
but there is great difficulty in understanding Al-
Sufi's description of the cluster. He says, "The
29th star (of Taurus) is the more northern of
the anterior side of the Pleiades themselves, and
the 30th is the southern of the same side ; the
31st is the following vertex of the Pleiades, and
is in the more narrow part. The 32nd is situated
outside the northern side. Among these stars, the
32nd is of the 4th magnitude, the others of the
5th." Now, it is very difficult or impossible to
identify these stars with the stars in the Pleiades
as they are at present. The brightest of all,
Alcyone (77 Tauri), now about 3rd magnitude, does
not seem to be mentioned at all by Al-Sufi ! as he
says distinctly that " the brightest star " (No 32
of Taurus) is "outside" the Pleiades "on the
northern side." It seems impossible to suppose
that Al-Sufi could have overlooked Alcyone had
it the same brightness it has now. The 32nd
star seems to have disappeared, or at least
diminished greatly in brightness, since the days
of Al-Sufi. More than four stars were, however,
seen by Al-Sufi, for he adds, " It is true that the
stars of the Pleiades must exceed the four

THE CONSTELLATIONS 255

mentioned above, but I limit myself to these four
because they are very near each other and the
largest [that is, the brightest] ; this is why I have
mentioned them, neglecting the others." A full
examination of the whole question is given by
Flammarion in his interesting work Les Etoiles
(pp. 289-307), and I must refer my readers to this
investigation for further details.

According to Brown, Simonides of Keos (B.C.
556-467) says, " Atlas was the sire of seven
daughters with violet locks, who are called the
heavenly Peleiades" l The name is by some
supposed to be derived from the Greek TrAetW,
full. The Old Testament word Kimah (Job ix. 9
and xxviii. 31) and Amos (v. 8) is derived from
the Assyrian Kimta, a " family." Aratus describes
the Pleiades in the following lines : —

" Near his 2 left thigh together sweep along
The flock of Clusterers. Not a mighty span
Holds all, and they themselves are dim to see,
And seven paths aloft men say they take,
Yet six alone are viewed by mortal eye.
These seven are called by name Alkyoni
Kelaini, Meropi and Steropi
Taygeti, Elecktri, Maia queen.
They thus together small and faint roll on
Yet notable at morn and eve through Zeus." 3

The Pleiades are mentioned by Ovid. Accord-
ing to the ancient poets they were supposed to

1 Primitive Constellations, vol. i. p. 143.

2 Perseus.

3 Heavenly Display, 254-8, 261-5, quoted by Brown in
Primitive Constellations, vol. i, p. 274.

256 ASTRONOMICAL CURIOSITIES

represent the children of Atlas and Hesperus, and
on this account they were called Atlantids or
Hesperides. From the resemblance in sound to
the word TrXctas, a pigeon, they were sometimes
called " the doves," and for the same reason the
word TrAeu/, to navigate, led to their being called
the "shipping stars." The word TrXctas was also
applied to the priestesses of the god Zeus (Jupiter)
at Dordona, in the groves of which temple there
were a number of pigeons. This is, perhaps,
what Aratus refers to in the last line of the
extract quoted above. According to Neapolitan
legends, the name of Virgil's mother was Maia.
The mother of Buddha, the Hindoo avatar, was
also named Maia. In Italy the Pleiades were
called Gallinata, and in France poussiniere, botli
of which mean the hen and chickens, a term also
given to them by Al-Sufi. The old Blackfoot
Indians called them " The Seven Perfect Ones."
The Crees and O jib way Indians called them the
" Fisher Stars." The Adipones of Brazil and
some other nations claimed that they sprang from
the Pleiades ! The Wyandot Indians called them
" The Singing Maidens."

Photographs show that the brighter stars of
the Pleiades are involved in nebulosity. That
surrounding Maia seems to be of a spiral form.
Now, there is a Sanscrit myth which represents
Maia as "weaving the palpable universe," for
which reason she was " typified as a spider."

THE CONSTELLATIONS 257

This seems very appropriate, considering the web
of nebulous light which surrounds the stars of
the group. Maia was also considered as a type
of the universe, which again seems appropriate,
as probably most of the stars were evolved from
spiral nebulae.

The name Hyades is supposed to be derived
from the Greek word veiv, to rain, because in
ancient times they rose at the rainy season.

In ancient Egypt, Aldebaran was called ary ;
and the Pleiades chooa, a word which means
" thousands." The name Aldebaran seems to
have been originally applied to the whole of the
Hyades group. Aldebaran was also called by
the Arabians al-fanik, the great Camel, and
the Hyades al-kilas, the young Camels. The two
close stars v and K Tauri were called al-kalbain,
the dogs of Aldebaran. La Condamine states that
the Indians of the Amazon saw in the Hyades the
head of a bull.

Gemini, the Twins, is the third constellation of
the Zodiac. It was also called Gemelli, etc.
According to Dupuis it represents the llth
" labour of Hercules "—his triumph over the dog
Cerberus.1 But some of Dupuis' ideas seem very
fanciful. The Twins are usually called Castor
and Pollux, but they were also called by the
ancient writers Apollo and Hercules ; Jason and
Triptolemus ; Amphion and Zethus ; and Theseus
1 Lalande's Astronomie, vol. iv. p. 493,

258 ASTRONOMICAL CURIOSITIES

and Peritheus. In Egypt they represented the
deities Horus and Hippocrates. Brown thinks that
the " Great Twins " were originally the sun and
moon, " who live alternately. As one is born the
other dies ; as one rises the other sets." l This
applies to the full moon, but does not seem
applicable to the other lunar phases.

Gemini was the constellation to which Dante
supposed himself transported when he visited the
stellar heavens.2 He says he was born under the
influence of this " sign."

Cancer, the Crab, is the next sign of the Zodiac.
In the Greek mythology it was supposed to have
been placed in the sky by Juno to commemorate
the crab which pinched the toes of Hercules in
the Lernsean marsh. The Greek name was rvftL.
According to Dupuis it represents the 12th
" labour of Hercules " — his capture of the golden
apples in the Garden of the Hesperides, which
were guarded by a Dragon. This Dragon is
Draco, which was also called Custos Hesperidum.3
But the connection between a crab and the myth
of the golden apples is not obvious — unless some
reference to " crab apples " is intended ! Among
the Romans, Cancer was consecrated to Mercury,
and by the ancient Egyptians to their god Anubis.

The well-known cluster in Cancer called the

1 Primitive Constellations, vol. i. p. 292.

2 Paradiso, xxii. 111.

3 Lalande's Astronomic, vol. iv. p. 493.

THE CONSTELLATIONS 259

P_raesape, Al-Sufi says, is " a little spot which
resembles a cloud, and is surrounded by four
stars, two to the west [77 and 6 Cancri] and two to
the east " [y and 8]. This cluster is mentioned by
Aratus, who calls it the "Manger." The word
Praesape is often translated " Beehive," but there
can be no doubt that it really means " Manger,"
referring to the stars y and 8 Cancri, which the
ancients called Aselli, the ass's colts. These were
supposed to represent the asses which in the war
of Jupiter against the Giants helped his victory
by their braying !

Admiral Smyth says in his Bedford Catalogue
(p. 202) that he found y and 8 Cancri both of 4th
magnitude ; but the photometric measures show
that 8 is now distinctly brighter than y. An
occultation of 8 Cancri by the moon is recorded as
having occurred on September 3, B.C. 240.

The fine constellation Leo, the Lion, is the next
" sign " of the Zodiac, and is marked by the well-
known "Sickle." According to Dupuis, it repre-
sents the first " labour of Hercules " — the killing
of the Nemselian lion. Manilius called it Nemaeus.
It was also called Janonus sidus, Bacchi sidus,
etc. The Greek name was ^xtp, pfX€V> or A^X0*-
In ancient Egypt, Leo was sacred to Osiris, and
many of the Egyptian monuments are ornamented
with lions' heads. It is stated in the Horapolla
that its appearance was supposed to announce the
annual rising of the Nile.

260 ASTRONOMICAL CURIOSITIES

Regulus (a Leonis) is the brightest and moat
southern of the stars in the " Sickle." Al-Sufi
says " it is situated in the heart and is of the 1st
magnitude. It is that which is called al-maliki,
the royal star. It is marked on the astrolabe as
kalb al-asad, the Heart of the Lion " (whence the
name Cor Leonis). Modern photometric measures
make it about 1'3 magnitude. It has an 8^
magnitude companion at about 177" distance
(Burnham) which is moving through space with
the bright star, and is therefore at probably the
same distance from the earth as its brilliant
primary. This companion is double (8*5, 12'5 :
3"'05, Burnham). The spectroscope shows that
Regulus is approaching the earth at the rate of
5J miles a second. Its parallax is very small —
about 0"'022, according to Dr. Elkin — which
indicates that it is at a vast distance from the
earth ; and its brightness shows that it must be a
sun of enormous size. Ptolemy called it /foo-iAto-Kos,
whence its Latin name Regulus, first used by
Copernicus as the diminutive of rex.1

The next constellation of the Zodiac is Virgo,
the Virgin. It was also called by the ancients
Ceres, Isis, Erigone, Fortuna, Concorda, Astrsea,
and Themis. The Greek name was <£a/xeVo>#. Ceres
was the goddess of the harvest. Brown thinks
that it probably represents the ancient goddess
Istar, and also Ashtoreth. According to Prof.
1 Bedford Catalogue, p. 225.

THE CONSTELLATIONS 261

Sayce it is the same as the Accadiaii sign of " the
errand of Istar, a name due to the belief that it
was in August that the goddess Astarte descended
into Hades in search of her betrothed, the sun
god Tammuz, or Adonis, who had been slain by
the boar's tusk." l The ear of corn (Spica) is
found on the ancient Egyptian monuments, and
is supposed to represent the fertility caused by
the annual rising of the Nile. According to
Aratus, the Virgin lived on earth during the
golden age under the name of Justice, but that in
the bronze age she left the earth and took up her
abode in the heavens.

" Justice, loathing that race of men,
Winged her flight to heaven."

The Sphinx near the Great Pyramid has the
head of a virgin on the body of a lion, represent-
ing the goddess Isis (Virgo) and her husband
Osiris (Leo).

Al-Sufi's 5th star of Virgo is Flamsteed 63
Virginis. Al-Sufi says it is a double star of the
5th magnitude. In Al-Sufi's time it formed a
" naked-eye double " with 61 Virginis, but owing
to large proper motion, 61 has now moved about
26 minutes of arc towards the south, and no
longer forms a double with 63. This interesting
fact was first pointed out by Flammarion in his
work Les EMles (p. 373).

1 Nature, April 6, 1882.

262 ASTRONOMICAL CURIOSITIES

Libra, the Balance, is one of the " signs " of the
Zodiac, but originally formed the claws of the
Scorpion. It was called Juguna by Cicero, and
Mochos by Ampelius. The Greek name was
<f>apiJ,ovO€. Virgil suggests that it represented the
justice of the emperor Augustus, honoured by
the name of a constellation; but probably this
refers to the birth of Augustus under the sign of
Libra, as Scaliger has pointed out. According to
Brown, "the daily seizing of the dying western
sun by the claws of the Scorpion of darkness is
reduplicated annually at the Autumnal Equinox,
when the feeble waning sun of shortening days
falls ever earlier into his enemy's grasp ; " l and
he says, " The Balance or Scales (Libra), which it
will be observed is in itself neither diurnal nor
nocturnal, is the only one of the zodiacal signs
not Euphratean in origin, having been imported
from Egypt and representing originally the
balance of the sun at the horizon between the
upper and under worlds ; and secondarily the
equality of the days and nights at the equinox." 2

According to Houzeau, Libra was formed at the
beginning of the second century B.C., and it does
not appear in any writings before those of
Geminus and Varron.3

1 Primitive Constellations, vol. i. p. C8.

2 Ibid., vol. i. p. 71.

3 Billiographie Generate de VAstronomie, vol. i. Introduction, pp.
131, 132.

THE CONSTELLATIONS 263

Milton says in Paradise Lost : —

" The Eternal to prevent such horrid fray,
Hung forth in heaven his golden scales, yet seen
Betwixt Astrsea and the Scorpion's sign."

(Here Astraea is Virgo.)

It is worth noticing that both Ptolemy and
Al-Sufi rated the star K Librae as two magnitudes
brighter than A. Librae. The two stars are now
practically of equal brightness (5th magnitude),
and it seems impossible to believe that this could
have been the case in Al-Sufi's time. Surely a
careful observer like Al-Sufi, who estimated the
relative brightness of stars to a third of a
magnitude, could not possibly have made an error
of two magnitudes in the brightness of two stars
near each other! It should be stated, however,
that K Librae was rated 5th magnitude by
Argelander and Heis, and A, 6th magnitude by
the same excellent observers.

The next "sign" of the Zodiac, Scorpion, was
consecrated by the Romans to Mars, and by the
Egyptians to Typhon.1 It was called Nepa by
Cicero, Martis sidus by Manilius, and Fera magna
by Aratus. The Greek name was Tra^oov.

Mr. E. B. Knobel has called attention to a
curious remark of Ptolemy with reference to the
bright star Antares (a Scorpii), " Media earum
quae tendit ad rapinam quae dicitur Cor Scor-
pionis " ; and he made a similar remark with
1 Lalande'a Astronomie, vol. i. p. 296.

264 ASTRONOMICAL CURIOSITIES

reference to Betelgeuse (a Orionis) and others.
But Mr. Robert Brown1 explains the remark by
the fact that in ancient times these stars rose in
the morning at a time when caravans were ex-
posed to dangers from robbers. Thus the term
had nothing to do with the aspect or colour of
these stars, but was merely a reference to their
supposed astrological influence on human affairs.

In the Egyptian Book of the Dead, Silkit was a
goddess who assumed the form of a scorpion in
the sky. She was supposed to be the daughter
of Ra.

With reference to stars " outside " the ancient
figure of Scorpio, the first, Al-Sufi says, " is a star
which immediately follows al-schaulat " [A] and K,
" it is of small 4th magnitude ; Ptolemy calls it
i/e^eAoa'Sr/s " [nebulous], Schjelerup, in his trans-
lation of Al-Sufi's work, does not identify this
object; but it is very evidently y Telescopii,
which lies exactly in the position described by
Al-Sufi. Now, it is a very interesting and curious
fact that Ptolemy called it nebulous, for in the
same telescopic field with it is the nebula h 3705
(= Dunlop 557). Dunlop describes it as a " small
well-defined rather bright nebula, about 20" in
diameter; a very small star precedes it, but is
not involved; following y Telescopii." Sir John
Herschel at the Cape found it fairly resolved into
very faint stars, and adds, " The whole ground
1 Primitive Constellations, vol. i. p. 74.

THE CONSTELLATIONS 265

of the heavens, for an immense extent is thickly
sown with such stars. A beautiful object." l
This perhaps accounts for the nebulous appearance
of the star as seen by Ptolemy.

Several novce or temporary stars are recorded
as having appeared in Scorpio. One in the year
B.C. 134 is stated by Pliny to have induced
Hipparchus to form his catalogue of stars. This
star was also observed in China. Its exact posi-
tion is unknown, but Flammarion thinks it may
possibly have appeared about 4° north of the star
ft Scorpii. Another new star is said to have
appeared in A.D. 393, somewhere in the Scorpion's
tail. One in A.D. 1203 and another in 1584 are
also mentioned, the latter near ir Scorpii.

The constellation Scorpio seems to be referred
to by Dante in his Purgatorio (ix. 4-6) in the
lines —

" De gemma la sua fronte era lucenta
Poste in figura del fredda animale
Che con la coda percota la genta,"

perhaps suggested by Ovid's remark —

" Soorpius exhibit caudaque menabitur unca." 2

Next to Scorpio comes Sagittarius, the Archer.
It is said to have been placed in the sky as a
symbol of Hercules, a hero who was held in the
greatest veneration by the ancient Egyptians.

1 Cape Observations, p. 116.
• Metamorphoses, xv, 371.

266 ASTRONOMICAL CURIOSITIES

The horse, usually associated with this constella-
tion, was a symbol of war. It was also called
by the ancients Chiron, Arciteiiens, Minotaurus,
Croton, etc. The Greek name was Trawi, or Tracovt.
Chiron was supposed to be the son of Saturn and
Phillyra, and first taught men to ride on horses.
The name is derived from the Greek x€t/P> a hand.
Some writers, however, think that Chiron is
represented by the constellation of the Centaur,
and others say that Sagittarius represents the
Minotaur loved by Persephone. According to
Dupuis, Sagittarius represents the 5th "labour
of Hercules," which consisted in hunting the
birds of the lake Stymphalus, which ravaged the
neighbouring countries. These birds are perhaps
represented by Cygnus, Altair, and the Vulture
(Lyra). The Lyre probably represents the
musical instrument which Hercules used to
frighten the birds.1

According to Al-Sufi, the Arabians called the
stars 7, 8, c, and rj Sagittarii which form a quadri-
lateral figure, "the Ostrich which goes to the
watering place," because they compared the Milky
Way to a river. They compared the stars o-, <£, T,
and £ Sagittarii, which form another quadri-
lateral, to an ostrich which has drunk and returns
from the " watering place." He says that the star
A Sagittarii forms with these two "ostriches" a
tent, and certainly the figure formed by A, <£, £, e,
1 Lalande's A&tronomie, vol. iv. p. 487.

THE CONSTELLATIONS 267

and 8 is not unlike a tent. Al-Sufi says more
about these " ostriches " ; but the ideas of the old
Arabians about the stars seem very fanciful.

A " temporary star " is recorded in the Chinese
Annals of Ma-touan-lin as having appeared in
May, B.C. 48, about 4° distant from /x Sagittarii.
Another in the year 1011 A.D. appeared near the
quadrilateral figure formed by the stars <r, T, £,
and <f> Sagittarii. This may perhaps be identified
with the object referred to by Hepidannus in the
year 1012, which was of extraordinary brilliancy,
and remained visible "in the southern part of
the heavens during three months." Another is
mentioned near the same place in A.D. 386 (April to
July).1 The number of " temporary stars " recorded
in this part of the heavens is very remarkable.

According to Brown, Sagittarius is depicted on
a stone, cir. B.C. 1100, found at Babilu, and now in
the British Museum.2

The next of the "signs of the Zodiac" is
Capricornus, the Goat. In the Arabo- Latin edition
of Ptolemy's Almagest it is called Alcaucurus. It
is supposed to represent Amalthea, the goat
which nursed Jupiter. According to Dupuis it
represented the 6th " labour of Hercules," which
was the cleaning out of the Augean stables.3

a.2 Capricorni is the northern of two stars of the

1 Monthly Notices, R.A.S., April 14, 1848.

- Prim. Co7ist., vol. ii. p. 45.

3 Lalande's Astronomic, pp, 472-3.

268 ASTRONOMICAL CURIOSITIES

4th magnitude (a and ft Capricorni). It really
consists of two stars visible to the naked eye.
The second of these two stars (c^) is not mentioned
by Al-Sufi, but I find that, owing to proper
motion, they were nearer together in his time
(tenth century), and were evidently seen by him
as one star, ft Capricorni (about 3rd magnitude)
is a very wide double star (3J, 6 ; 205"), which
may be seen with any small telescope. The
fainter star was found to be a close double by
Burnham. At present ft is brighter than a,
although rated of the same brightness by Al-Sufi.
Aquarius is the next " sign of the Zodiac." It
is supposed to represent a man pouring water out
of an urn or bucket. Other names given to this
constellation were Aristaeus, Ganymede, Cecrops,
Amphora, Uriia, and Aqua tyrannus. According
to Dupuis it represents the 7th "labour of
Hercules," which was his victory over the famous
bull which ravaged Crete.1 But the connection
between a bull and a bucket is not obvious.
Aquarius is represented in several places on the
Egyptian monuments. Some of the ancient poets
supposed that it represented Deucalion (the Noah
of the Greek story of the Deluge) ; others thought
that it represented Cecrops, who came to Greece
from Egypt, built Athens, and was also called
Bifornis. Others say that he was Ganymede, the
cup-bearer of the gods.

1 Lalande's Astronomic, vol. iv. p. 485,

THE CONSTELLATIONS 269

There is some difficulty about the identification
of some of Al-Sufi's stars in Aquarius. His sixth
star (Fl. 7) is nearly 10° south-west of ft Aquarii,
and is, Al-Sufi says, " the following of three stars
in the left hand, and precedes the fourth [/?]
... it is of the 6th magnitude. Ptolemy calls it
third, but in reality it is very faint " [now about
6th magnitude]. The seventh [//,] is the middle
one of the three and about 4J magnitude, although
Al-Sufi calls it "small fifth " [Ptolemy rated it 4].
The eighth star, e, is the preceding of the three
and about 3*8, agreeing closely with Al-Sufi's 4*3.
Ptolemy rated it 3. This star is mentioned
under the name nou in the time of Tcheou-Kong
in the twelfth century B.C. Al-Sufi says, " These
three stars are followed by a star of the 5th
magnitude which Ptolemy has not mentioned. It
is brighter than the sixth star" [Fl. 7], This
is evidently v Aquarii. If, however, we plot
Ptolemy's positions as given by Al-Sufi, it seems
probable that Ptolemy's sixth star was really v,
and that either /u, or Fl. 7 was not seen by him.
As Ptolemy called his seventh star 4th magni-
tude, and his sixth and eighth stars 3rd magnitude,
some considerable change of brightness seems to
have taken place in these stars ; as v is now only
4J and Fl. 7 only a bright sixth. Variation was
suspected in Fl. 7 l by Gould. I found it very

1 This star is not shown in Proctor's small Atlas, but it lies
between /* and v, nearer to /*.

270 ASTRONOMICAL CURIOSITIES

reddish with binocular in October, 1892. Burnham
found it to be a close double star, the companion
being about 12th magnitude at a distance of only
2". It is probably a binary.

According to Al-Sufi, the Arabians called the
second and third stars of the figure (a and o Aquarii)
sad al-malik (malk or mulfc), " the Good Fortune
of the king." They called the fourth and fifth stars
(ft and £ Aquarii) with the twenty-eighth star of
Capricornus (c) sad al-sund, " the Good Fortune of
the Happy Events/' " This is the 24th mansion of
the moon." These stars rose at the time of year
when the cold ends, and they set at the time the
heat ends. Hence, Al-Sufi says, " when they rise the
rains begin, and when they set the unhealthy winds
cease, fertility abounds, and the dew falls." Hence
probably the Arabic names. This, of course,
applies to the climate of Persia and Arabia, and
not to the British Isles. Al-Sufi says, " They call
the 6th, 7th, and 8th stars sad bula, ' The Good
Fortune which swallows up ! ' This is the 23rd
mansion of the moon. They say that it is so
called because that at the time of the Deluge it
rose at the moment when God said, * O earth !
absorb the waters ' (Koran, chap, xi., v. 46). They
called the stars y, TT, £, and 17 Aquarii sad al-
achbija, ( the Good Fortune of the tents ' ; this is
the 25th mansion of the moon, and they give
them this name because of these four stars,
three form a triangle, the fourth [£] being in the

THE CONSTELLATIONS 271

middle." The three were considered to form a
tent.

The Arabians called the bright star Fomalhaut
"in the mouth of the southern fish al-dhifda
al~auval, « the first Frog,' as the bright one on the
southern point of the tail of Kitus [Cetus] is called
al-dhifda al-tsani [ft Ceti], * the second Frog.' "
Fomalhaut was also called al-zhalim, "the male
ostrich."

Al-Sufi says, " Some of the Arabians state that
a ship is situated to the south of Aquarius." The
stars in the Southern Fish (Piscis Australis) seem
to be here referred to.

The constellation Pisces, the Fishes, is the last
of the " signs of the Zodiac." The Fishes appear
on an ancient Greek obelisk described by Pococke.
Among the Greeks this sign was consecrated to
Venus ; and in Egypt to Nepthys, wife of Typhon
and goddess of the sea. Pisces is said to end the
Zodiac as the Mediterranean Sea terminated Egypt.
This idea was suggested by Schmidt, who also
conjectured that the Ram (Aries) was placed at
the beginning of the Zodiac because Thebes, a
town sacred to Jupiter t Ammon, was at the begin-
ning of Egypt in ancient times ; and he thought
that the constellation Triangulum, the Triangle,
represented the Nile Delta, Eridanus being the
Nile.1 The constellation was represented in
ancient times by two fishes connected by a cord
1 Lalande's Astronomic, vol. i. p. 247.

272 ASTRONOMICAL CURIOSITIES

tied to their tails. The southern of these " fishes "
lies south of the " Square of Pegasus," and the
northern between Andromeda and Aries. Accord-
ing to Manilius, the origin of these fishes is as
follows : Venus, seeing Typhon on the banks of
the river Euphrates, cast herself with her son into
the river and they were transformed into fishes !

Some of the Arabians substituted a swallow for
the northern of the two fishes — the one below
Andromeda. The swallow was a symbol of
Spring. According to Dupuis, Pisces represents
the 8th "labour of Hercules," his triumph over
the mares of Diomed which emitted fire from their
nostrils.1 But the connection between fishes and
mares is not obvious, and some of Dupuis' ideas
seem very fanciful. Here he seems to have found
a " mare's nest."

The constellation Cetus, the Whale, represents,
according to ancient writers, the sea monster sent
by Neptune to devour Andromeda when she was
chained to the rock. Aratus calls Cetus the
" dusky monster," and Brown remarks that " the
* Dusky Star ' would be peculiarly appropriate to
Mira (the wondrous o Ceti)." 2 Cetus was also
called Canis Tritonis, or Dog of the Sea, Bayer in
his Atlas (1603) shows a dragon instead of a whale,
finding it so represented on some ancient spheres.
Al-Sufi calls it Kitus or K^TOS, the whale. He says,

1 Lalande's Astronomic, vol. iv. p. 489.

2 Primitive Constellations, vol. i. p. 91.

THE CONSTELLATIONS 273

"it "is" represented by the figure of a marine
animal, of which the fore part is turned towards
the east, to the south of the Ram, and the hinder
part towards the west behind the three ' extern '
stars of Aquarius."

Al-Sufi does not mention the variable star
o Ceti, now called Mira, or the " wonderful," nor
does he refer to any star in its immediate vicinity.
We may, therefore, conclude that it was near a
minimum of light at the time of his observation of
the stars of Cetus.

The constellation of Orion, one of the finest in
the heavens, was called by Al-Sufi al-djabbar, " the
Giant," and also al-djauza, " the Spouse." The poet
Longfellow says —

" Sirius was rising in the east
And, slow ascending one by one,
The kindling constellations shone
Begirt with many a blazing star
Stood the great giant Al-gebar
Orion, hunter of the beast !
His sword hung gleaming at his side
And on his arm, the lion's hide —
Scattered across the midnight air
The golden radiance of its hair."

Al-Sufi says it " is represented by the figure of
a standing man, to the south of the sun's path.
This constellation very much resembles a human
figure with a head and two shoulders. It is called
al-djabbar, ' the Giant,' because it has two thrones,
holds a club in his hand, and is girded with a
sword." Orion is supposed to have been a son of

274 ASTRONOMICAL CURIOSITIES

Neptune ; but there are many stories of the origin
of the name. It is also said to be derived from
the Greek word wpa, because the constellation was
used to mark the different times of the year.
According to the ancient fable, Orion was killed
by a scorpion, and was placed in the sky at the
request of Diana. According to Houzeau, the
name comes from oriri, to be bom. Scorpio rises
when Orion sets, and he thinks that the idea of
the ancients was that the Scorpion in this way
kills the giant Orion.

In ancient Egypt Orion was called Sahu. This
name occurs on the monuments of the Ptolemies,
and also on those of the Pharaohs. It is also
mentioned in the Book of the Dead. It seems
to have been considered of great importance in
ancient Elgypt, as its heliacal rising announced
that of Sirius, which heralded the annual rising
of the Nile.

The constellation Eridanus lies south of Taurus,
east of Cetus, and west of Lepus. In ancient
times it was supposed to represent the Nile or the
Po. Ptolemy merely calls it liora^ov do-Tcpwr/ios, or
asterism of the river. It was called Eridanus by
the Greeks, and Pluvius by the Romans. It
appears to correspond with the Hebrew Shicor.
Al-Sufi calls it al-nahr, " the River."

One of the most interesting points in Al-Sufi' s
most interesting work is the identity of the
bright star known to the ancient astronomers as

THE CONSTELLATIONS 275

aohir al-nahr, " the End of the River," and called
by Ptolemy 'Eo^a-ros roO Trora/xov, " the Last in the
River." Some astronomers have identified this
star with a Eridani (Achernar), a bright southern
star of the 1st magnitude, south of Eridanus.
But Al-Sufi's description shows clearly that the
star he refers to is really 0 Eridani; and the
reader will find it interesting to follow his descrip-
tion with a star map before him. Describing
Ptolemy's 34th star of Eridanus (the star in
question), he says, " the 34th star is found before
[that is west of] these three stars [the 31st, 32nd,
and 33rd, which are v2, Du, and v' in Proctor's
Atlas], the distance between it and that of the
three which is nearest being about 4 cubits [9° 20'].
It is of the first magnitude; it is that which
is marked on the southern astrolabe, and called
twhir al-nahr, ' the End of the River.' There are
before this bright one two stars, one to the south,
[s Eridani, not shown in Proctor's small Atlas],
the other to the north [t Eridani] ; Ptolemy does
not mention these. One of these stars is of the
4th magnitude, the other of the 5th. There is
behind the same [that is, east of it] a star of the
4th magnitude distant from it two cubits
[c Eridani]. To the south of the three stars which
follow the bright one there are some stars of the
4th and 5th magnitudes, which he [Ptolemy] has
not mentioned."
Now, a glance at a star map of this region will

276 ASTRONOMICAL CURIOSITIES

show clearly that the bright star referred to by
Al-Sufi is undoubtedly 0 Eridani, which is there-
fore the star known to the ancients as the " End
of the River," or the " Last in the River."

The position given by Ptolemy agrees fairly
well with Al-Sufi' s description, although the place
is slightly erroneous, as is also the case with
Fomalhaut and ft Ceiitauri. It is impossible to
suppose that either Ptolemy or Al-Sufi could
have seen a Eridani, as it is too far south to be
visible from their stations, and, owing to the
precession of the equinoxes, the star was still
further south in ancient times. Al-Sufi says
distinctly that the distance between Ptolemy's
33rd star (which is undoubtedly h Eridani, or
Proctor's v) and the 34th star was " 4 cubits,"
or 9° 20'. The actual distance is about 9° 11', so
that Al-Sufi's estimate was practically correct.
Halley, in his Catalogus Stellarium Australium,
identifies Ptolemy's star with 6 Eridani, and Baily
agreed with him.1 Ulugh Beigh also identifies
the "Last in the River" with 6 Eridani. The
Arabic observer Mohammed AH Achsasi, who
observed in the seventeenth century, called 0 Eri-
dani Achr al-nahr, and rated it first magni-
tude.2 To argue, as Bode and Flammarion have
done, that Ptolemy and Al-Sufi may have heard
of a Eridani from travellers in the southern

1 Memoirs, R.A.S., vol. xiii. 61.

2 Monthly Notices, R.A.S., June, 1895.

THE CONSTELLATIONS 277

hemisphere, is to beg the whole question at issue.
This is especially true with reference to Al-Sufi,
who says, in the preface to his work, that he has
described the stars " as seen with my own eyes."
a Eridani is over 11 "cubits" from h Eridani
instead of " 4 cubits " as Al-Sufi says. This shows
conclusively that the star seen by Al-Sufi was
certainly not a Eridani. The interest of the
identification is that Al-Sufi rated 6 Eridani of
the first magnitude, whereas it is now only 3rd
magnitude ! It was measured 3*06 at Harvard
and estimated 3*4 by Stanley Williams, so that it
has evidently diminished greatly in brightness
since Al-Sufi' s time. There is an interesting
paper on this subject by Dr. Anderson (the dis-
coverer of Nova AurigaB and Nova Persei) in
Knowledge for July, 1893, in which he states that
the " Last in the River," according to the state-
ments of Hipparchus and Ptolemy, did rise above
their horizon at a certain time of the year, which
a Eridani could not possibly have done. This
seems sufficient to settle the question in favour
of 6 Eridani. Dr. Anderson says, " It is much to
be regretted that Professor Schjellerup, the able
and industrious translator of Sufi, has allowed
this to escape his notice, and helped in the preface
and note to his work to propagate the delusion
that a Eridani is Ptolemy's ' Last in the River ' " ;
and in this opinion I fully concur. Al-Sufi's clear
account places it beyond a doubt that the star

278 ASTRONOMICAL CURIOSITIES

known to Hipparchus, Ptolemy, Al-Sufi, and
Ulugh Beigh as the "Last in the River" was
0 Eridani. 0 must have diminished greatly in
brightness since Al-Sufi's time, for in ranking it
as 1st magnitude he placed it in a very select
list. He only rated thirteen stars in the whole
heavens as being of the 1st magnitude. These
are : Arcturus, Vega, Capella, Aldebaran, Regulus,
/3 Leonis, Fomalhaut, Rigel, 6 Eridani, Sirius,
Procyon, Canopus, and a Centauri. All these
stars were actually seen by Al-Sufi, and described
from his own observations. He does not mention
a Eridani, as it was not visible from his station in
Persia.

6 Eridani is a splendid double star (3'40, 4'49 :
8"'38, 1902, Tebbutt). I found the components
white and light yellow with 3-inch refractor in
the Punjab. Dr. Gould thinks that one of the
components is variable to some extent. This is
interesting, considering the brilliancy of the star
in Al-Sufi's time. The brighter component was
found to be a spectroscopic binary by Wright, so
that on the whole the star is a most interesting
object.

The small constellation Lepus, the Hare, lies
south of Orion. Pliny calls it Dasypus, and Virgil
Auritus. In ancient Egypt it was the symbol of
vigilance, prudence, fear, solitude, and speed.1 It
may perhaps represent the hare hunted by Orion ;
1 Lalande's Astronomic, vol. i. p. 274.

THE CONSTELLATIONS 279

but some say it was placed in the sky to com-
memorate a terrible plague of hares which
occurred in Sicily in ancient times.

A little north-west of the star p. Leporis is
Hind's " crimson star" (R.A. 4h 53m, S. 11° 57', 1900)
described by him as " of the most intense crimson,
resembling a blood drop on the background of
the sky; as regards depth of colour, no other
star visible in these latitudes could be compared
with it." It is variable from about the 6th to
the 8th magnitude, with a period of about 436
days from maximum to maximum.

The constellation Canis Major, the Great Dog,
is remarkable for containing Sirius, the brightest
star in the heavens. In the Greek mythology
it was supposed to represent a dog given by
Aurora to Cephalus as the swiftest of all dogs.
Cephalus wished to match it against a fox
which he thought surpassed all animals for speed.
They both ran ;for so long a time, so the story
goes, that Jupiter rewarded the dog by placing
it among the stars. But probably the dog comes
from Anubis, the dog-headed god of the ancient
Egyptians. According to Brown, Theogirius (B.C.
544) refers to the constellation of the Dog.1 He
thinks that Canis Major is probably "a reduplica-
tion" of Orion; Sirius and ft Canis Majoris corre-
sponding to a and y Orionis ; 8, 22, and c Cards
Majoris to the stars in Orion's belt (8, €, and
1 Primitive Constellation*, vol. i. p. 143.

280 ASTRONOMICAL CURIOSITIES

£ Orionis) ; and -rj and K Canis Major is with K and
ft Orionis.1

The Arabic name of Sirius was al-schira, which
might easily be corrupted into Sirius. The
Hebrew name was Sihor. According to Plutarch,
the Ethiopians paid regal honours to the Celestial
Dog. The Romans vised to sacrifice a dog in its
honour at the fetes called Robigalia, which were
held on the seventh day before the Calends of
May, and nine days after the entry of the sun
into Taurus. Pliny says, "Hoc tempus Varro
determinat sole decimam partem Tauri obtinenti
quod canis occidit, sidus per se vehemens," etc.'2

Owing to some remarks of Cicero, Horace, and
Seneca, it has been supposed that in ancient times
Sirius was of red colour. Seneca says, "Nee
mirum est, si terra omnis generis et varia evapo-
ratio est; quam in coelo quoque 11011 unus
appareat color rerum, sed acrior sit Caiiiculse
rubor, Nartis remissior, Jovis nullus, in lucem
puram nitore perducto."3 It is now brilliantly
white with a bluish tinge. But this change of
colour is somewhat doubtful. The remarks of
the ancient writers may possibly refer to its
great brilliancy rather than its colour. Al-Sufi
says nothing about its colour, and it was probably

1 Primitive Constellations, vol. i. p. 278.

2 Lalande's Astronomie, vol. iv. p. 468.

3 Queest. Nat., Lib. 1, Cap. I. § 6; quoted by Dr. See. " Cani-
cula" is Sirius, and " Nartis," Mars.

THE CONSTELLATIONS 281

a white star in his time. If it were red in his
day he would most probably have mentioned the
fact, as he does in the case of several red stars.
Brown, however, quotes the folloAving from Ibn
Alraqqa, an Arabian observer : —

"I recognize Sirius shining red, whilst the morning is becoming

white.

The night fading away, has risen and left him,
The night is not afraid to lose him, since he follows her."

Schjellerup thinks that it is very doubtful that
Sirius was really red as seen by Hipparchus and
Ptolemy. But in an exhaustive inquiry made by
Dr. See on the supposed change of colour,1 he
comes to the conclusion that Sirius was really red
in ancient times. Seneca states distinctly that
it was redder than Mars (see extract above), and
other ancient writers refer to its red colour. It
has been generally supposed that the Arabian
astronomer Alfraganus, in his translation of
Ptolemy's Almagest, refers to only five red stars
observed by Ptolemy, namely, Arcturus, Aldebaran,
Betelgeuse, Antares,, and Pollux. But Dr. See
shows that this idea is due to a mistranslation of
Alfraganus by Plato Tibertinus in 1537, and that
Ptolemy did not speak of "five red stars," but
five nebulous stars, as stated by Christmann and
Golius. Ptolemy described Sirius as vVoVippo?,
"fiery red," the same word used with reference
to the other stars mentioned above. The change
1 Astronomy and Jttfap&jftfar, vol. 11, 1892.

282 ASTRONOMICAL CURIOSITIES

of colour, if any, probably took place before
Al-Sufi's time.
Dr. See says —

"Prof. Newcomb rejects the former well-
authenticated redness of Sirius, because he
cannot explain the fact. But the ink was
scarcely dry on his new book on the stars, in
which he takes this position, when Nova Persei
blazed forth in 1901 ; and observers saw it change
colour from day to day and week to Aveek. Could
any one explain the cause of these numerous and
conspicuous changes of colour? Shall we, then,
deny the changes of colour in Nova Persei, some
of which were noticed when it was nearly as
bright as Sirius?"1

On the ceiling of the Memnonium at Thebes the
heliacal rising of Sirius is represented under the
form and name of Isis. The coincidence of this
rising with the annual rising of the Nile is men-
tioned by Tibullus and Aclian. About 4000 B.C.
the heliacal rising of Sirius coincided with the
summer solstice (about June 21) and the begin-
ning of the rising of the Nile. The festival in
honour of this event was held by the Egyptians
about July 20, and this marked the beginning
of the sacred Egyptian year. On the summit
of Mount Pelion in Thessaly there was a temple
dedicated to Zeus, where sacrifices were offered
at the rising of Sirius by men of rank who were
chosen for the purpose by the priests and wore
fresh sheepskins.

1 The Observatory, April, 1906, p. 175.

THE CONSTELLATIONS 283

Sirius seems to have been worshipped by the
ancient Egyptians under the name of Sothis, and
it was regarded as the star of Isis and Osiris.
The last name without the initial O very much
resembles our modern name.

According to Al-Sufi, the Arabians called Sirius
al-schira al-abur, " Sirius which has passed across,"
also al-schira al Jamdnija, " the Sirius of Yemen."
He says it is called al-abtir, " because it has passed
across the Milky Way into the southern region."
He relates a mythological story why Sirius " fled
towards the south" and passed across the Milky
Way towards Suhail (Canopus). The same story
is told by Albufaragius l (thirteenth century).
(The story was probably derived from Al-Sufi.)
Now, it seems to me a curious and interesting
fact that the large proper motion of Sirius would
have carried it across the Milky Way from the
eastern to the western border in a period of
60,000 years. Possibly the Arabian story may
be based on a tradition of Sirius having been seen
on the opposite, or eastern, side of the Milky Way
by the men of the early Stone Age. However
this may be, we know from the amount and
direction of the star's proper motion that it must
have passed across the Milky Way from east to
west within the period above stated. The Arabic
name al-abrtr is not, therefore, a merely fanciful

1 Houzeau, Bibliographie Generate de V Astronomic, vol. i.,
Introduction, p. 129.

284 ASTRONOMICAL CURIOSITIES

one, but denotes an actual fact. The proper
motion of Sirius could not possibly have been
known to the ancients, as it was only revealed by
accurate modern observations.

The little constellation Cams Minor, the Little
Dog, lies south of Gemini and Cancer. Small as
it is, it was one of the original forty-eight con-
stellations of Ptolemy. In the Greek mythology
it was supposed to represent either one of Diana's
hunting dogs, or one of Orion's hounds. Ovid calls
it the dog of Icarus. Others say it was the
dog of Helen, who was carried off by Paris.
According to the old poets, Orion's dog, or the dog
of Icarus, threw himself into a well after seeing
his master perish. The name Fovea, given to the
constellation by Bayer, signifies a pit where corn
was deposited. This comes from the fact that
the rising of the star Procyoii (a Canis Minoris)
indicated the season of abundance. But Lalande
thought it more probable that the idea of a pit
came from the Greek o-etpos, which means a corn
store, and that it was confounded with Sirius.

The name of the bright star Procyon (a Canis
Minoris) is derived from the Greek TrpoKtW, " the
advanced day," because it appeared in the morning
sky before Sirius. Procyon was called by the
Hindoos Hanouman after their famous monkey
god, from whose tail a bridge is said to have been
formed to enable the army of Rama to pass from
India to Ceylon. Al-Sufi says that the star was

THE CONSTELLATIONS 285

marked on the old astrolabes as al-schira al-
schamia, " the Syrian Sirius." It was also called,
he says, al-schira al-gumaisa, " the Sirius with
blear eyes"(!) from weeping because Sirius had
passed across the Milky Way, Procyon remaining
on the eastern side. Here we have the same
legend again. The proper motion of Procyon
(about the same in amount and direction as that
of Sirius) shows that the star has been on the
eastern side of the Milky Way for many ages
past. About 60,000 years hence, Procyon wrill be
near the star 0 Canis Major is, and will then — like
Sirius — have passed across the Milky Way.

Argo, the Ship, is a large constellation south of
Hydra, Monoceros, and Canis Major. It is called
by Al-Sufi al-safina, " the Ship." It is supposed to
represent the first ship ever built. The name is
derived from the builder Argo, or from the Greek
word 'Apyos. This ship is said to have been built
in Thessaly by order of Minerva and Neptune, to
go on the expedition for the conquest of the
golden fleece. The date of this expedition, com-
manded by Jason, is usually fixed at 1300 or
1400 B.C. With reference to the position of
this supposed ship in the sky, Proctor says,
" It is noteworthy that when we make due
correction for the effects of precession during the
past 4000 years, the old constellation Argo is
set on an even keel, instead of being tilted
some 45° to the horizon, as at present when

286 ASTRONOMICAL CURIOSITIES

due south." He connects Argo with Noah's
Ark.

The brightest "star of Argo is Canopus, called
Suha'il by Al-Sufi. It is the second brightest star-
in the heavens ; but it is not visible in northern
latitudes. The Harvard photometric measures make
it nearly one magnitude brighter than the zero
magnitude, about two magnitudes brighter than
Aldebaran, and about half the brightness of Sirius.
This fine star has been suspected of variable light.
Webb says, "It was thought (1861) in Chili
brighter than Sirius." Observing it in the
Punjab, the present writer found it on several
occasions but little inferior to Sirius, although
very low on the southern horizon. From recent
observations by Mr. H. C. McKay in Australia, he
believes that it is variable to the extent of at least
half a magnitude.1 But it is difficult to establish
variations of light in very bright stars. The
parallax of Canopus is very small, so its distance
from the .earth is very great, and it must be a sun
of gigantic size. According to Al-Fargani, Canopus
was called the star of St. Catherine by the
Christian pilgrims in the tenth century ,a It
was called Suhail by the old Arabians, a name
apparently derived from the root sahl, " a plain " ;
and Schjellerup suggests that the name was
probably applied to this and some other southern

1 English Mechanic, March 25, 1904, p. 145.

2 Humboldt's Cosmos, vol. iii. p. 185, footnote (Otte's translation).

THE CONSTELLATIONS 287

stars because they seem to move along a plain
near the southern horizon. Al-Sufi says that he
measured the latitude of Schiraz in Persia, where
he observed, and found it to be 29° 36' ; and hence
for that place Canopus, when on the meridian, had
an altitude of about 9°. Canopus was the ancient
name of Aboukir in Egypt, and is said to have
derived its name from the pilot of Menelaus, whose
name was Kanobus, and who died there from the
bite of a snake. The star is supposed to have
been named after him, and it was worshipped by
the ancient Egyptians.

Al-Sufi does not mention the famous variable
star 77 ArgCis, which, owing to the precession of
the equinoxes, he might possibly have seen close
to the horizon, if it had been a bright star in his
day. It lies between <j> Velorum and a Crucis.
Both of these stars are mentioned by Al-Sufi, but
he says nothing of any bright star (or indeed any
star) between them. This negative evidence tends
to show that i; Argus was not visible to the naked
eye in Al-Sufi's time. This extraordinary star
has in modern times varied through all degrees
of brightness from Sirius down to the 8th magni-
tude I Schonf eld thought that a regular period is
very improbable. It seems to be a sort of connect-
ing link between the long period variables and the
novce or temporary stars. It is reddish in colour,
and the spectrum of its light is very similar to
that of the temporary stars. Whether it will

288 ASTRONOMICAL CURIOSITIES

ever become a brilliant object again, time alone
can tell ; but from the fact that it was presumably
faint in Al-Sufi's time, and afterwards increased
to the brightness of Sirius, it seems possible that
its light may again revive.

The long constellation Hydra lies south of
Cancer, Leo, Crater, Corvus, Virgo, and Libra.
It was also called Asina, Coluber, Anguis, Subli-
matus, etc. In the Greek mythology it was
supposed to represent the Lernsean serpent killed
by Hercules. According to Ovid, who fixed its
acroiiycal rising for February 14, it had a common
origin with Corvus and Crater. Apollo, wishing
to sacrifice to Jupiter, sent the Crow with a cup to
fetch water. On his way to the well the Crow
stopped at a fig tree and waited for the fruit to
ripen I Afterwards, to excuse his delay, he said
that a serpent had prevented him from drawing
the water. But 'Apollo, to punish the Crow for
his deception, changed his plumage from white to
black, and ordered the serpent to prevent the
Crow from drinking.1 Hydra WSLS called by Al-
Sufi al-schudja, " the Serpent, or Hydra." He says
that " it contains twenty-five stars in the figure
and two ' outside,' and its head is to the south of the
southern scale of the Balance" (a Librse). But
this is clearly a mistake (one of the very few
errors to be found in Al-Sufi's work), for he goes on
to say that the head is composed of four stars
1 Lalande's Astronomic, vol. i. p, 277 4

THE CONSTELLATIONS 289

forming a figure like the head of a horse, and he
adds, "This head is in the middle between
al-shira al-guniaisa [Procyon] and Kalb al-asad
[Regulus] the Heart, inclining from these two
stars a little to the south." This clearly indicates
the stars 8, c, 17, and a- Hydrse which, with
£ Hydrse, have always been considered as forming
the Hydra's head. These stars lie south of a and
/? Cancri, not south of Libra as Al-Sufi says (doubt-
less by a slip of the pen).

Ptolemy's 12th star of Hydra (a Hydrse) is,
Al-Sufi says, " the bright red star which is found
at the end of the neck where the back begins ; it is
of the 2nd magnitude. It is that which is marked
011 the astrolabe as unk al-schudja, 'the neck
of the serpent,' also al-fard, ' the solitary one.' "
Al-Sufi's estimate of its brightness agrees well
with modern measures ; but it has been suspected
of variable light. Sir John Herschel's estimates
at the Cape of Good Hope varied from 1*75 to 2*58
magnitude. He thought that its apparent varia-
tion might be due to its reddish colour, and com-
pares it to the case of a Cassiopeise. But as this
latter star is now known to be irregularly variable
it seems probable that a Hydrse may be variable
also. Gemmill found it remarkably bright on
May 9, 1883, when he thought it nearly equal to
Pollux (1*2 magnitude). On the other hand,
Franks thought it nearer the 3rd than the 2nd
magnitude en March 2, 1878. On April 9, 1884, the

290 ASTRONOMICAL CURIOSITIES

present writer found it only slightly less than
Regains (1'3 magnitude). On April 6, 1886, how-
ever, it was considerably less than Regulus, but
half a magnitude brighter than ft Canis Minoris,
or about 2J magnitude. In the Chinese Annals it
is called the " Red Bird." In a list of thirty stars
found on a tablet at Birs-Nimroud, it is called
" The son of the supreme temple." Although to the
naked eye deserving the name of Alphard or " the
solitary one," it is by no means an isolated star
when examined with a telescope. It has a faint
and distant companion, observed by Admiral
Smyth ; and about 25' to the west of it Ward saw
a small double star (8, 13 : 90° : 50"). With a 3-inch
refractor in the Punjab, I saw a small star of
about 8 J magnitude to the south and a little east
of the bright star, probably identical with Smyth's
companion. Farther off in the same direction I
saw a fainter star, and others at greater distances
in the field. There is also a faint star a little to
the north. I also saw Ward's double with the
3-inch telescope.

There is some difficulty in identifying the stars
numbered by Ptolemy 13, 14, and 15 in Hydra.
Having plotted a map 'from Ptolemy's positions
(as given by Al-Sufi), I have come to the conclu-
sion that Ptolemy's stars are 13 = K Hydrae ;
14 = v ; and 15 = A Hydrse, probably. From the
clear description given by Al-Sufi of the stars
observed by him, I find that his stars are 13 = v, ;

THE CONSTELLATIONS 291

14 = v.2 ; and 15 = A. Hydras. We must, therefore,
conclude that Ptolemy and Al-Sufi saw only three
stars where now there are four,1 and that
K HydrsB was not seen, or at least is not men-
tioned by Al-Sufi. K is, therefore, probably vari-
able. It was rated 4 by Tycho Brahe, Bayer, and
Hevelius; it is at present about 5th magnitude.
If Ptolemy did not see v2 it is probably variable
also, and, indeed, it has been suspected of variable
light.2

The small constellation of Crater, the Cup, lies
north of Hydra, and south of Leo and Virgo.
Al-Sufi calls it al-batija, "the Jar, or Cup." He
says the Arabians called it al-malif, " the Crib, or
Manger." According to Brown, the stars of Crater
exactly form a Bakhiaii KavOapos, with its two
handles rising above the two extremities of the
circumference.3 An Asia Minor legend " connected
Crater with the mixing of human blood with wine
in a bowl." Crater is referred to by Ovid in the
lines —

" Dixit et antiqui monumenta perenuia facti
Anguis, Avis, Crater sidera, juncta micunt."

The star a Crateris was rated 4th magnitude by

1 This was pointed out by Flammarion in hia work Les Etoiks,
page 532; but bis identifications do not agree exactly with
mine.

2 See Proctor's Map 7, now x.

3 Primitive Constellations , vol. i, p. IOC.

292 ASTRONOMICAL CURIOSITIES

Al-Sufi and all other observers, and the Harvard
measures make it 4*20, a satisfactory agreement.
It has three companions noted by Admiral Smyth.
One of these he called " intense blood colour."
This is R Crateris, now known to be variable
from above the 8th magnitude to below the 9th.
Sir John Herschel called it an " intense scarlet
star, a curious colour." With 3-inch refractor in
the Punjab I found it " full scarlet." It is one of
an open pair, the further of the two from a.
There is a third star about 9th magnitude a little
south of it. Ward saw a 13th magnitude star
between a and R with a 2f -inch (Wray) refractor.
This I saw " readily " with my 3-inch. Smyth
does not mention this faint star, although he
used a much larger telescope.

Corvus, the Crow, is a small constellation, north
of Hydra. Aratus says "the Crow form seems
to peck the fold of the water snake" (Hydra).
The victory which Valerius Corvinus is said to
have owed to a crow has given it the name of
Pomptina, because the victory took place near
the Pontine marshes.1 A quadrilateral figure is
formed by its four brightest stars, y, S, /?, and
e Corvi. This figure has sometimes been mistaken
for the Southern Cross by those who are not
familiar with the heavens. But the stars of the
Southern Cross a re much brighter.

The constellation Ceiitaurus, the Centaur, lies
1 Lalaflde's Astronomic, vol. i. p. 278.

THE CONSTELLATIONS 293

south of Hydra and Libra, and north of the
Southern Cross. According to Dupuis, Centaurus
represents the 3rd "labour of Hercules," his
triumph over the Centaurs.1 The Centaurs were
supposed to be a people living in the vicinity of
Mount Ossa, who first rode on horses. The con-
stellation was also called Semivir, Chiron, Phobos,
Minotaurus, etc. Al-Sufi says it " is represented
by the figure of an animal, of which the forepart
is the upper part of a man from the head to end
of the back, and its hinder part is the hinder part
of a horse, from the beginning of the back to the
tail. It is to the south of the Balance [Libra]
turning its face towards the east, and the hinder
part of the beast towards the west."

Al-Sufi describes very clearly the four bright
stars of the famous " Southern Cross." Owing
to precession these stars were some 7° further
north in the tenth century than they are at
present, and they could have been all seen by
Al-Sufi, when on the meridian. In the time of
Ptolemy and Hipparchus, they were still further
north, and about 5000 years ago they were visible
in the latitude of London. Dante speaks of these
four stars as emblematical of the four cardinal
virtues, Justice, Temperance, Fortitude, and
Prudence.

Closely south-east of a and /? Crucis is the dark
spot in the Milky Way known as the " Coal Sack,'
1 Lalande's Astronomic, vol. iv,

294 ASTRONOMICAL CURIOSITIES

which forms such a conspicuous object near the
Southern Cross. It was first described by Pinzon
in 1499 ; and afterwards by Lacaille in 1755.
Although to the naked eye apparently black,
photographs show that it contains many faint
stars, but, of course, much less numerous than
in the surrounding regions. The dark effect is
chiefly caused by contrast with the brilliancy
of the Milky Way surrounding it.

Al-Sufi also mentions the bright stars a and
/? Centauri which follow the Southern Cross. He
says that the distance between them " is four
cubits," that is about 9° 20', but it is less than this
now. a has a large " proper motion " of 3"'67 per
annum, and was farther, from /3 in Al-Sufi's time
than it is at present. This, however, would not
wholly account for the difference, and Al-Sufi's
over-estimate is probably due to the well-known
effect by which the distance between two stars
is apparently increased when they are near the
horizon. Several of Al-Sufi's distances between
southern stars are over-estimated, probably for
the same reason.

The constellation Lupus, the Wolf, is south of
Libra and Scorpio. It lies along the western
border of the Milky Way. According to ancient
writers it represents Lycaon, King of Arcadia,
a contemporary of Cecrops, who is said to have
sacrificed human victims, and 011 account of his
cruelty was changed into a wolf. Another fable

THE CONSTELLATIONS 295

is that it represents a wolf sacrificed by the
Centaur Chiron. According to Brown, Lupus
appears on the Euphratian planisphere discovered
by George Smyth in the palace of Sennacherib.
Al-Sufi called it al-sabu, "the Wild Beast." It
was also called al-fand, "the Leopard," and al-
asada, " the Lioness."

Ara, the Altar, lies south of Scorpio. According
to ancient writers it represents an altar built by
Vulcan, when the gods made war against the
Titans. It is called by Al-Sufi al-midjman, " the
Scent Box," or "the Altar."

The little constellation Corona Australis, the
Southern Crown, lies south and west of Sagittarius,
east of Scorpio, and west of Telescopium.
Aratus refers to the stars in Corona Australis
as—

" Other few

Before the Archer under his forefeet
Led round in circle roll without a name." 2

But the constellation was known by the names
Caduceus, Orbiculus, Corona Sagittarii, etc. The
ancient poets relate that Bacchus placed this
crown in the sky in honour of his mother Semele.3
Others say that it represents the crown conferred
on Corinne of Thebes, famous as a poet.

The small constellation Piscis Australis, or the

1 Primitive Constellations, vol. i. p. 112.

2 Ibid., vol. i. p. 113.

3 Lalande's Astronomie, vol. i.

296 ASTRONOMICAL CURIOSITIES

Southern Fish, lies south of Capricornus and
Aquarius. In the most ancient maps it is repre-
sented as a fish drinking the water which flows
from the urn of Aquarius.

A good many constellations have been added
to the heavens since the days of Al-Sufi, and
notes on some of these may be of interest.

CAMELOPABDALIS. — This constellation first
appears on a celestial planisphere published by
Bartschius in the year 1624. It was not formed
by Bartschius himself, but by the navigators of
the sixteenth century. It lies south of Ursa
Minor, north of Perseus and Auriga, east of
Draco, and west of Cassiopeia. It contains no
star brighter than the 4th magnitude.

LYNX. — This constellation is south of Camelo-
pardalis and Ursa Major, and north of Gemini
and Cancer. It was formed by Hevelius in 1660,
and he called it the Lynx, because, he said, it
contained only faint stars and " it was necessary
to have the eyes of a lynx " to see them ! Some
of them were, however, observed by Ptolemy and
Al-Sufi, and are mentioned by the latter under
Ursa Major.

CANES VENATICI, or the Hunting Dogs.— This
was formed by Hevelius in 1660. It lies south of
the Great Bear's tail, north of Coma Berenices, east
of Ursa Major, and west of Bootis. Its brightest
stars a (12) and /3 (8) were observed by Al-Sufi,

THE CONSTELLATIONS 297

and included by him in the " extern " stars of Ursa
Major.

COMA BERENICES. — This constellation lies be-
tween Canes Venatici and Virgo. Although it
was not included among the old forty-eight
constellations of Ptolemy, it is referred to by
Al-Sufi as the Plat, or Tress of Hair, and he in-
cluded its stars Flamsteed 12, 15, and 21 in the
" extern " stars of Leo. It was originally formed
by the poet Callimachus in the third century B.C.,
but was not generally accepted until reformed by
Hevelius. Callimachus lived at Alexandria in the
reigns of Ptolemy Philadelphus and Ptolemy
Euergetes, and was chief librarian of the famous
library of Alexandria from about B.C. 260 until his
death in B.C. 240. Eratosthenes was one of his
pupils. The history of the constellation is as
follows : Berenice, wife of Ptolemy Euergetes, made
a vow, when her husband was leaving her on a
military expedition, that if he returned in safety
she would cut off her hair and consecrate it in the
temple of Mars. Her husband returned, and she
fulfilled her vow. But on the next day the hair
had disappeared — stolen from the temple — and
Conon the mathematician showed Ptolemy seven
stars near the constellation of the Lion which did
not belong to any constellation. These were
formed into a constellation and called Berenice's
Hair. Conon is referred to by Catullus in the
lines —

298 ASTRONOMICAL CURIOSITIES

" Idem me ille Conon coeleste numine vidit
E. Berenice vertice Caesariem."

Coma Berenices first occurs as a distinct con-
stellation in the catalogue contained in the
Rudolphine Tables formed by Kepler (epoch 1600)
from the observations of Tycho Brahe.1 Bayer
substituted a sheaf of corn, an idea derived from
an ancient manuscript.

LEO MINOR. — This small constellation lies be-
tween Ursa Major and Leo, and east of the
Lynx. It was formed by Halley about the year
1660 ; but is referred to by Al-Sufi, who includes
one of its stars (PI. 41) in the " extern " stars of
Leo. There are, however, several brighter stars
in the group. The brightest, PI. 46, was measured
3-92 at Harvard. The star PI. 37 was called
prcecipua (or brightest) by Tycho Brahe, and
rated 3, but as it was measured only 4'77 at
Harvard it may possibly have diminished in
brightness.

SEXTANS. — This constellation lies south of Leo,
and north and east of Hydra. It was formed by
Hevelius about the year 1680. According to the
Harvard photometric measures its brightest star
is PI. 15 (4-50).

MONOCEROS, or the Unicorn, lies south of Gemini

and Canis Minor, north of Canis Major and Argo,

east of Orion, and west of Hydra. It appears

on the planisphere of Bartschius, published in

1 W. T. Lynn in The Observatory, vol. 22, p. 236.

THE CONSTELLATIONS 299

1624. According to Scaliger it is shown on an
old Persian sphere. One of its stars, Fl. 22, is
mentioned by Al-Sufi among the " extern " stars
of Canis Major (No. 1). Another, Fl. 30, is given
under Hydra (" Extern " No. 1) and Fl. 8, 13, and
15 are apparently referred to in Gemini. The star
15 Monocerotis is a little south of £ Geminorum,
and was measured 4*59 magnitude at Harvard.
It was at one time supposed to be variable with
a short period (about 3| days), but this variation
has not been confirmed. The spectrum is of the
fifth type — with bright lines — a very rare type
among naked-eye stars. It is a triple star (5,
8-8, 11-2: 2"'9, 16"'3) and should be seen with a
4-inch telescope. It has several other small
companions, one of which (139°*2 : 75"*7) has been
suspected of variation in light. It was estimated
8J by Main in 1863, but only 12 by Sadler in 1875.
Observing it on March 28, 1889, with 3-inch
refractor, I found it about one magnitude
brighter than a star closely preceding, and esti-
mated it 8 or 8| magnitude. It is probably
variable and should be watched.

SCUTUM SOBIBSKI. — This is, or was, a small
constellation in the southern portion of Aquila,
which was formed by Hevelius in 1660 in honour
of the Polish hero Sobieski. Its principal stars,
which lie south-west of X Aquilae, were mentioned
by Al-Sufi and are referred to by him under that
constellation. It contains a very bright spot of

300 ASTRONOMICAL CURIOSITIES

Milky Way light, which may be well seen in the
month of July just below the star A. Aquilse.
Closely south of the star 6 Aquilae is a remarkable
variable star R Scuti (R.A. 18h 42nu2, S. 5° 49'). It
varies from 4'8 to 7*8 with an irregular period.
All the light changes can be observed with a good
opera-glass.

VULPECULA, the Fox. — This modern constella-
tion lies south of Cygnus, north of Sagitta and
Delphinus, east of Hercules, and west of Pegasus.
It was formed by Hevelius in 1660. One of its
stars, 6 Vulpeculae, is mentioned by Al-Sufi in
describing the constellation Cygnus. Closely
north-west of 32 Vulpeculae is the short-period
variable T Vulpeculae. It varies from 5*5 to 6'2
magnitude, and its period is 4*436 days. This is
an interesting object, and all the changes of light
can be observed with an opera-glass.

LACEBTA. — This little constellation lies south
of Cepheus and north of Pegasus. Its formation
was first suggested by Roger and Anthelm in 1679,
and it was called by them " The Sceptre and the
Hand of Justice." It was named Lacerta by
Hevelius in 1690, and this name it still retains.
Al-Sufi seems to refer to its stars in his description
of Andromeda, but does not mention any star
in particular. It brightest star Fl. 7 (a Lacertse)
is about the 4th magnitude. About one degree
south-west of 7 is 5 Lacertse, a deep orange star
with a blue companion in a fine field.

THE CONSTELLATIONS 301

There are some constellations south of the
Equator which, although above Al-Sufi's horizon
when on the meridian, are not described by him,
as they were formed since his time. These are as
follows : —

SCULPTOR. — This constellation lies south of
Aquarius and Cetus, and north of Phoenix. Some
of its stars are referred to by Al-Sufi under
Eridanus as lying within the large triangle
formed by /? Ceti, Fomalhaut, and a Phosnicis.
The brightest star is a, about 12° south of /? Ceti
(4*39 magnitude Harvard). About 7° south-east
of a is the red and variable star R Sculptoris ;
variable from 6*2 to 8*8 magnitude, with a period
of about 376 days. Gould describes it as "in-
tense scarlet." It has a spectrum of the fourth
type.

PHCENIX. — This constellation lies south of
Sculptor. Some of its stars are referred to by
Al-Sufi, under Eridanus, as forming a boat-shaped
figure. These are evidently a, *, /*, /?, v, and y.
a is at the south-eastern angle of Al-Sufi's triangle
referred to above (under "Sculptor"). (See
Proctor's Atlas, No. 3.)

FORNAX, the Furnace, lies south of Cetus, west
of Eridanus, and east of Sculptor and Phoenix.
It was formed by Lacaille, and is supposed to
represent a chemical furnace with an alembic
and receiver! Its brightest star, a Fornacis, is
identical with 12 Eridani. j

302 ASTRONOMICAL CURIOSITIES

C^ELUM, the Sculptor's Tools, is a small constel-
lation east of Columba, and west of Eridanus. It
was formed by Lacaille. The brightest stars are
a and y, which are about 4-J magnitude, a has a
faint companion ; and y is a wide double star to
the naked eye.

ANTLIA, the Air Pump, lies south of Hydra,
east and north of Argo, and west of Centaur us.
It was formed by Lacaille. It contains no star
brighter than 4th magnitude. The brightest, a,
has been variously rated from 4 to 5, and Stanley
Williams thinks its variability " highly probable."

NOBMA, the Rule, lies south of Scorpio. It
contains no star brighter than the 4th magnitude.

TELESCOPIUM. — This modern constellation lies
south of Corona Australis, and north of Pavo.
Its stars a, 8, and £, which lie near the northern
boundary of the constellation, are referred to by
Al-Sufi in his description of Ara.

MICBOSCOPIUM. — This small constellation is south
of Capricornus, and west of Piscis Australis. Its
stars seem to be referred to by Al-Sufi as having
been seen by Ptolemy, but he does not specify
their exact positions. It contains no star brighter
than 4-| magnitude.

South of Al-SufTs horizon are a number of
constellations surrounding the south pole, which,
of course, he could not see. Most of these have
been formed since his time, and these will now be

THE CONSTELLATIONS 303

considered; beginning with that immediately
surrounding the South Pole (Octans), and then
following the others as nearly as possible in order
of Right Ascension.

OCTANS. — This is the constellation surround-
ing the South Pole of the heavens. There is no
bright star near the Pole, the nearest visible to
the naked eye being <r Octantis, which is within
one degree of the pole. It was estimated 5*8 at
Cordoba. The brightest star in the constellation
is v Octantis (a, Proctor), which lies about 12
degrees from the pole in the direction of Indus
and Microscopium. The Harvard measure in
3*74 magnitude.

HYDRUS, the Water-Snake, is north of Octans
in the direction of Achernar (a Eridani). The
brightest star is /?, which lies close to 0 Octantis.
The Harvard measure is 2*90. Gould says its
colour is " clear yellow." It has a large proper
motion of 2"-28 per annum. Sir David Gill found
a parallax of 0"*134, and this combined with the
proper motion gives a velocity of 50 miles a
second at right angles to the line of sight,
y Hydri is a comparatively bright star of about
the 3rd magnitude, about 15 J degrees from the
South Pole. It is reddish, with a spectrum of the
third type.

HOROLOGIUM, the Clock, is north of Hydra, and
south of Eridanus. Three of its stars, a, 8, and ^,
at the extreme northern end of the constellation,

304 ASTRONOMICAL CURIOSITIES

seem to be referred to by Al-Sufi in his descrip-
tion of Eridanus, but he does not give their exact
positions. Most of the stars forming this constel-
lation were below Al-Sufi' s horizon.

RETICULUM, the Net, is a small constellation
to the east of Hydrus and Horologiurn. The
brightest star of the constellation is a (3'36
Harvard, 3'3 Cordoba, and "coloured").

DORADO, the Sword Pish, lies east of Reticulum
and west of Pictor. It contains only two stars
brighter than the 4th magnitude. These are a (3*47
Harvard) and ft '(3*81 Harvard, but suspected of
variation). About 3° east of a Reticuli is the
variable star R Doradus. It varies from 4*8 to
6'8, and its period is about 345 days. Gould calls
it " excessively red." It may be followed through
all its fluctuations of light with an opera-glass.

MENSA, or Mons Mensa, the Table Mountain, lies
between Dorado and the South Pole, and repre-
sents the Table Mountain of the Cape of Good
Hope. It contains no star brighter than the 5th
magnitude.

PICTOR, the Painter's Easel, lies north of
Doradus, and south of Columba. It contains no
very bright stars, the brightest being a (3*30
Harvard).

VOLANS, the Flying Fish, is north of Mensa, and
south and west of Argo. Its brighter stars, with
the exception of a and (3, form an irregular six-
sided figure. Its brightest star is ft (3'65) according

THE CONSTELLATIONS 305

to the Harvard measures. The Cordoba estimates,
however, range from 3*6 to 4'4, and Gould says
its colour is " bright yellow." Williams rated
it 3-8.

CHAM^LION. — This small constellation lies south
of Volans, and north of Mensa and Octans. None
of its stars are brighter than the 4th magni-
tude, its brightest being a (4'08 Harvard) and
y (4-10).

ARGO. — This large constellation extends much
further south than Al-Sufi could follow it. The
most southern star he mentions is e Carinae, but
south of this are several bright stars, ft Carinse
is T80 according to the Harvard measures;
v Carinse, 3'08 ; 0, 3'03 ; <o, 3*56 ; and others. A
little north-west of t is the long-period variable
R Caring (9h 29™'7, S. 62° 21', 1900). It varies from
4*5 at maximum to 10 at minimum, and the period
is about 309*7 days. A little east of R Carinse is
another remarkable variable star, I Carinae
(R.A. 9h 42m'5, S. 62° 3'). It varies from 3'6 to 5'0
magnitude, with a period of 35| days from
maximum to maximum. All the light changes
can be observed with an opera-glass, or even
with the naked eye. It was discovered at
Cordoba. The spectrum is of the solar type (G).

MUSCA, the Bee, is a small constellation south
of the Southern Cross and Centaurus. Its
brightest stars are a (2'84 Harvard) and /3
(3*26). These two stars form a fine pair south of

306 ASTRONOMICAL CURIOSITIES

a Crucis. Closely south-east of a is the short-
period variable R Muscse. It varies from 6*5 to
7*6 magnitude, and its period is about 19 hours.
All its changes of light may be observed with a
good opera-glass.

APUS, the Bird of Paradise, lies south-east of
Musca, and north of Octans. Its brightest star
is a, about the 4th magnitude. Williams calls it
" deep yellow." About 3° north- west of a, in the
direction of the Southern Cross, is 6 Apodis, which
was found to be variable at Cordoba from 5J to
6|-. The spectrum is of the third type, which
includes so many variable stars.

TBIANGULUM AUSTBALIS, the Southern Triangle,
is a small constellation north of Apus, and south
of Norma. A fine triangle, nearly isosceles, is
formed by its three bright stars, a, /?, y, the
brightest a being at the vertex. These three stars
form with a Centauri an elongated cross. The
stars ft and y are about 3rd magnitude. /3 is
reddish, c (4*11, Harvard) is also reddish, and is
nearly midway between {$ and y, and near the
centre of the cross above referred to. a is a fine
star (1*88 Harvard) and is one of the brightest
stars in the sky — No. 33 in a list of 1500 highest
stars given by Pickering. About 1° 40' west of c
is the short-period variable R Trianguli Australis
(R.A. 15h 10m'8, S. 66° 8') discovered at Cordoba in
1871. It varies from 6*7 to 7'4, and the period is
about 3d 7h*2. Although not visible to ordinary

THE CONSTELLATIONS 307

eyesight it is given here, as it is an interesting
object and all its light changes may be well seen
with an opera-glass. A little south-east of ft is
another short-period variable, S Trianguli Australis
(R.A. 15h 52m'2, S. 63° 30'), which varies from 6'4 to
7*4, with a period of 6'3 days ; and all its fluctua-
tions of light may also be observed with a good
opera-glass.

CIRCINUS, the Compass, is a very small con-
stellation lying between Triangulum and
Centaurus. Its brightest star, a, is about 3J
magnitude, about 4° south of a Centauri.

PAVO, the Peacock, lies north of Octaiis
and Apus, and south of Telescopium. Its
brightest star is a, which is a fine bright star
(2*12 Harvard). K is a short-period variable. It
varies from 3*8 to 5*2, and the period is about 9
days. This is an interesting object, as all the
fluctations of light can be observed by the naked
eye or an opera-glass, c Pavonis was measured
4*10 at Harvard, but the Cordoba estimates vary
from 3'6 to 4'2. Gould says " it is of a remarkably
blue colour."

INDUS. — This constellation lies north of Octans,
and south of Sagittarius, Microscopium, and Grus.
One of its stars, a, is probably referred to by
Al-Sufi in his description of Sagittarius ; it lies
nearly midway between (3 Sagittarii and a Gruis,
and is the brightest star of the constellation. The
star « Indi (4*74 Harvard) has a remarkably large

308 ASTRONOMICAL CURIOSITIES

proper motion of 4"'68 per annum. Its parallax is
about 0"'28, and the proper motion indicates a
velocity of about 49 miles a second at right angles
to the line of sight.

TOUCAN. — This constellation lies north of Octans,
and south of Phoenix and Grus, east of Indus, and
west of Hydrus. Its brightest star is a, of about
the 3rd magnitude.

There are seven " celestial rivers " alluded to by
the ancient astronomers : —

1. The Fish River, which flows from the urn of
Aquarius.

2. The " River of the Bird," or the Milky Way
in Cygiius.

3. The River of the Birds — 2, including Aquila.

4. The River of Orion — Eridanus.

5. The River of the god Marduk — perhaps the
Milky Way in Perseus.

6. The River of Serpents (Serpens, or Hydra).

7. The River of Gaii-gal (The High Cloud)—
probably the Milky Way as a whole.

There are four serpents represented among the
constellations. These are Hydra, Hydrus, Serpens,
and Draco.

According to the late Mr. Proctor the date of
the building of the Great Pyramid was about 3400
B.C.1 At this time the Spring Equinox was in

1 Knowledge, May 1, 1889. Sir John Herschel, however, gives
3970 B.C.

THE CONSTELLATIONS 309

Taurus, and this is referred to by Virgil. But
this was not so in Virgil's time, when — on account
of the precession of the equinoxes — the
equinoctial point had already entered Pisces, in
which constellation it still remains. At the date
8400 B.C. the celestial equator ran along the whole
length of the constellation Hydra, nearly through
Procyon, and a little north of the bright red star
Antares.

The star Fomalhaut (a Piscis Australis) is inte-
resting as being the most southern 1st magnitude
star visible in England, its meridian altitude
at Greenwich being little more than eight
degrees.1

With reference to the Greek letters given to the
brighter stars by Bayer (in his Atlas published in
1603), and now generally used by astronomers,
Mr. Lynn has shown that although "Bayer did
uniformly designate the brightest stars in each
constellation by the letter a," 2 it is a mistake to
suppose — as has often been stated in popular
books on astronomy — that he added the other
Greek letters in order of brightness. That this
is an error clearly appears from Bayer's own
" Explicatio " to his Atlas, aud was long since
pointed out by Argelander (1832), and by Dr.
Gould in his Uranometria Argentina. Gould says,

1 The Observatory, November 1907, p. 412.

2 This is* not, however, invariably the case, as pointed out by
Mr. Denning in The Observatory, 1885, p. 340.

310 ASTRONOMICAL CURIOSITIES

" For the stars of each order, the sequence of the
letters in no manner represents that of their
brightness, but depended upon the positions of the
stars in the figure, beginning usually at the head,
and following its course until all the stars of that
order of magnitude were exhausted." Mr. Lynn
says, "Perhaps one of the most remarkable in-
stances in which the lettering is seen at a glance not
to follow the order of the letters is that of the three
brightest stars in Aquila [Al-Sufi's * three famous
stars'], 7 being evidently brighter than /?. But
there is no occasion to conjecture from this that
any change of relative brightness has taken place.
Bayer reckoned both of these two of the third
magnitude, and appears to have arranged ft before
7, according to his usual custom, simply because fi
is in the neck of the supposed eagle, and 7 at the
root of one of the wings." l Another good example
is found in the stars of the " Plough," in which the
stars are evidently arranged in the order of the
figure and not in the order of relative brightness.
In fact, Bayer is no guide at all with reference to
star magnitudes. How different Al-Sufi was in
this respect !

The stars Aldebaran, Regulus, Aiitares, and
Fomalhaut were called royal stars by the ancients.
The reason of this was that they lie roughly about
90° apart, that is 6 hours of Right Ascension. So,
if through the north and south poles of the
1 The Observatory, vol. 8 (1885), pp. 24G-7.

THE CONSTELLATIONS 311

heavens and each of these stars we draw great
circles of the sphere, these circles will divide the
sphere into four nearly equal parts, and the
ancients supposed that each of these stars ruled
over a quarter of the sphere, an idea probably
connected with astrology. As the position of
Aldebaran is R.A. 4h 30m, Declination North 16° 19',
and that of Antares is R.A. 16h 15m, Declina-
tion South 25° 2', these two stars lie at nearly
opposite points of the celestial sphere. From
this it follows that our sun seen from Aldebaran
would lie not very far from Antares, and seen
from Antares it would appear not far from
Aldebaran.

The following may be considered as represen-
tative stars of different magnitudes. For those of
first magnitude and fainter I have only given
those for which all the best observers in ancient
and modern times agree, and which have been
confirmed by modern photometric measures. The
Harvard measures are given : —

Brighter than "zero magnitude" Sirius (-1-58); Canopus

(-0-86)

Zero magnitude a Centauri (O'OG)

0 to 0-4 magnitude Vega (0-14); Capella

(0-21) ; Arcturus (0-24) ;

Rigel (0-34)

0-5 magnitude Procyon (0-48)

1st „ Aldebaran (1-OC)

2nd , a Persei (1-90) ; 0 Aurigse

(2-07)

312 ASTRONOMICAL CURIOSITIES

3rd magnitude , Bootis (3-08); £ Capri-

corni (2-98)

4th » p Leonis (3'85) ; A Scorpii

(4-16);7Crateris(4'14);
p Herculis (4-14)

5th » o Pegasi (4-85) ; ^ Capri-

corn! '5'10)

CHAPTER XX

The Visible Universe

SOME researches on the distribution of stars
in the sky have recently been made at
the Harvard Observatory (U.S.A.). The
principal results are : — (1) The number of stars
on any " given area of the Milky Way is about
twice as great as in an equal area of any other
region." (2) This ratio does not increase for
faint stars down to the 12th magnitude. (3)
" The Milky Way covers about one-third of the
sky and contains about half of the stars." (4)
There are about 10,000 stars of magnitude 6'6 or
brighter, 100,000 down to magnitude 8*7, one
million to magnitude 11, and two millions to
magnitude 11*9. It is estimated that there are
about 18 millions of stars down to the 15th
magnitude visible in a telescope of 15 inches
aperture.1

According to Prof. Kapteyn's researches 011
stellar distribution, he finds that going out from
the earth into space, the " star density" — that is,
1 Harvard College Observatory Annals, vol. xlviii. No. 5

314 ASTRONOMICAL CURIOSITIES

the number of stars per unit volume of space — •
is fairly constant until we reach a distance of
about 200 "light years." From this point the
density gradually diminishes out to a distance of
2500 " light years," at which distance it is reduced
to about one-fifth of the density in the sun's
vicinity.1

In a letter to the late Mr. Proctor (Knowledge,
November, 1885, p. 21), Sir John Herschel sug-
gested that our Galaxy (or stellar system) " con-
tained within itself miniatures of itself." This
beautiful idea is probably true. In his account
of the greater " Magellanic cloud," Sir John
Herschel describes one of the numerous objects
it contains as follows : —

" Very bright, very large ; oval ; very gradually
pretty, much brighter in the middle ; a beautiful
nebula ; it has very much the resemblance to the
Nubecula Major itself as seen with the naked eye,
but it is far brighter and more impressive in its
general aspect as if it were doubled in intensity.
Note — July 29, 1837. I well remember this obser-
vation, it was the result of repeated comparisons
between the object seen in the telescope and the
actual iiubecula as seen high in the sky on the
meridian, and no vague estimate carelessly set
down. And who can say whether in this object,
magnified and analysed by telescopes infinitely
superior to what we now possess, there may not
exist all the complexity of detail that the nubecula
itself presents to our examination ? " 2

1 Popular Astronomy, vol. 15 (1907), p. 529.

2 Cape Observation?, p. 77.

THE VISIBLE UNIVERSE 315

The late Lord Kelvin, in a remarkable address
delivered before the Physical Science Section of
the British Association at its meeting at Glasgow
in 1901, considered the probable quantity of
matter contained in our Visible Universe. He
takes a sphere of radius represented by the
distance of a star having a parallax of one-
thousandth of a second (or about 3000 years'
journey for light), and he supposes that uniformly
distributed within this sphere there exists a mass
of matter equal to 1000 million times the sun's
mass. With these data he finds that a body
placed originally at the surface of the sphere
would in 5 million years acquire by gravita-
tional force a velocity of about 12J miles a second,
and after 25 million of years a velocity of about
67 miles a second. As these velocities are of the
same order as the observed velocities among the
stars, Lord Kelvin concludes that there is probably
as much matter in our universe as would be
represented by a thousand million suns. If we
assumed a mass of ten thousand suns the velocities
would be much too high. The most probable
estimate of the total number of the visible stars
is about 100 millions ; so that if Lord Kelvin's
calculations are correct we seem bound to assume
that space contains a number of dark bodies.
The nebulae, however, probably contain vast
masses of matter, and this may perhaps account
— partially, at least — for the large amount of

316 ASTRONOMICAL CURIOSITIES

matter estimated by Lord Kelvin. (See Chapter
on"Nebulge.")

In some notes on photographs of the Milky
Way, Prof. Barnard says with reference to the
great nebula near p Ophiuchi, "The peculiarity
of this region has suggested to me the idea that
the apparently small stars forming the ground
work of the Milky Way here, are really very
small bodies compared with our own sun " ; and
again, referring to the region near ft Cygni, " One
is specially struck with the apparent extreme
smallness of the general mass of the stars in this
region." Again, with reference to x Cygni, he
says, " The stars here also are remarkably uniform
in size." l

Eastman's results for parallax seem to show that
"the fainter rather than the brighter stars are
nearest to our system." But this apparent paradox
is considered by Mr. Monck to be very misleading ; 2
and the present writer holds the same opinion.

Prof. Kapteyn finds " that stars whose proper
motions exceed 0"*05 are not more numerous in
the Milky Way than in other parts of the sky ;
or, in other words, if only the stars having proper
motions of 0"*05 or upwards were mapped, there
would be no aggregation of stars shoAving the
existence of the Milky Way." 3

* Monthly Notices, R. A.S., March, 1899.

2 Nature, February 13, 1890.

3 Popular Astronomy, vol. 15 (1907), p. 530.

THE VISIBLE UNIVERSE 317

With reference to the number of stars visible
on photographs, the late Dr. Isaac Roberts

says —

" So far as I am able at present to judge, under
the atmospheric conditions prevalent in this
country, the limit of the photographic method
of delineation will be reached at stellar, or
nebular, light of the feebleness of about 18th-
magiiitude stars. The reason for this inference
is that the general illumination of the atmosphere
by starlight concentrated upon a film by the
instrument will mask the light of objects that are
fainter than about 18th-magnitude stars." l

With reference to blank spaces in the sky, the
late Mr. Norman Pogson remarked —

" Near S Ophiuchi we find one of the most re-
markable vacuities in this hemisphere — an elliptic
space of about 65' in length in the direction of
R.A., and 40' in width, in which there exists no
star larger than the 13th magnitude ... it is im-
possible to turn a large telescope in that direction
and, if I may so express it, view such black dark-
ness, without a feeling that we are here searching
into the remote regions of space, far beyond the
limits of our own sidereal system." 2

Prof. Barnard describes some regions in the
constellation Taurus containing "dark lanes" in
a groundwork of faint nebulosity. He gives two
beautiful photographs of the regions referred to,
and says that the dark holes and lanes are

1 Photographs of Star-Clusters and Nebulx, vol. ii. p. 17.

2 Monthly Notices, K.A.S., May 9, 1856.

318 ASTRONOMICAL CURIOSITIES

apparently darker than the sky in the immediate
vicinity. He says, "A very singular feature in
this connection is that the stars also are absent
in general from the lanes." A close examination
of these photographs has given the present writer
the impression that the dark lanes and spots are in
the nebulosity, and that the nebulosity is mixed
up with the stars. This would account for the
fact that the stars are in general absent from the
dark lanes. For if there is an intimate relation
between the stars and the nebulosity, it would
follow that where there is no nebulosity in this
particular region there would be no stars. Prof.
Barnard adds that the nebulosity is easily visible
in a 12-inch telescope.1

With reference to the life of the universe, Prof.
P. R. Moulton well says —

" The lifetime of a man seems fairly long, and
the epoch when Troy was besieged, or when the
Pharaohs piled up the pyramids in the valley of
the Nile, or when our ancestors separated on the
high plateaux of Asia, seems extremely remote,
but these intervals are only moments compared
to the immense periods required for geological
evolutions and the enormously greater ones con-
sumed in the developement of worlds from widely
extended nebulous masses. We recognize the
existence of only those forces whose immediate
consequences are appreciable, and it may be that
those whose effects are yet unseen are really of
the highest importance. A little creature whose

1 AstropTiysical Journal, vol. 25 (1907), p. 219.

THE VISIBLE UNIVERSE 319

life extended over only two or three hours of a
summer's day might be led, if he were sufficiently
endowed with intelligence, to infer that passing
clouds were the chief influence at work in chang-
ing the climate instead of perceiving that the
sun's slow 'motion across the sky would bring
on the night and its southward motion the
winter." *

In a review of my book Astronomical Essays
in The Observatory, September, 1907, the follow-
ing words occur. They seem to form a good
and sufficient answer to people who ask, What
is there beyond our visible universe? "If the
stellar universe is contained in a sphere of
say 1000 stellar units radius, what is there
beyond ? To this the astronomer will reply that
theories and hypotheses are put forward for the
purpose of explaining observed facts ; when there
are no facts to be explained, no theory is required.
As there are no observed facts as to what exists
beyond the farthest stars, the mind of the
astronomer is a complete blank on the subject.
Popular imagination can fill up the blank as it
pleases." With these remarks I fully concur.

In his address to the British Association, Prof.
G. H. Darwin (now Sir George Darwin) said —

" Man is but a microscopic being relatively to
astronomical space, and he lives on a puny planet
circling round a star of inferior rank. Does it not,
then, seem futile to imagine that he can discover

1 Popular Astronomy, vol. 11 (1903), p. 293.

320 ASTRONOMICAL CURIOSITIES

the origin and tendency of the Universe as to
expect a housefly to instruct us as to the theory
of the motions of the planets ? And yet, so long .
as he shall last, he will pursue his search, and will
110 doubt discover many wonderful things which
are still hidden. We may indeed be amazed at all
that man has been able to find out, but the
immeasurable magnitude of the undiscovered will
throughout all time remain to humble his pride.
Our children's children will still be gazing and
marvelling at the starry heavens, but the riddle
will never be read."

The ancient philosopher Lucretius said —

" Globed from the atoms falling slow or swift
I see the suns, I see the systems lift
Their forms ; and even the system and the suna
Shall go back slowly to the eternal drift." 1

But it has been well said that the structure
of the universe " has a fascination of its own for
most readers quite apart from any real progress
which may be made towards its solution." 2

The Milky Way itself, Mr. Stratoiioff considers
to be an agglomeration of immense condensations,
or stellar clouds, which are scattered round the
region of the galactic equator. These clouds, or
masses of stars, sometimes leave spaces between
them, and sometimes they overlap, and in this
way he accounts for the great rifts, like the Coal
Sack, which allow us to see through this great

1 Translated by W. H. Mallock, Nature, February 8, 1900,
p. 352.

2 Howard Payn, Nature, May 16, 1901, p. 56.

THE VISIBLE UNIVERSE

circle of light. He finds other condensations of
stars ; the nearest is one of which our sun is a
member, chiefly composed of stars of the higher
magnitudes which " thin out rapidly as the Milky
Way is approached," There are other condensa-
tions : one in stars of magnitudes 6*5 to 8*5 ; and
a third, farther off, in stars of magnitudes 7 '6 to 8.
These may be called opera-glass, or field-glass
stars.

Stratonoff finds that stars with spectra of the
first type (class A, B, C, and D of Harvard) which
include the Sirian and Orion stars, are principally
situated near the Milky Way, while those of type
II. (which includes the solar stars) " are principally
condensed in a region coinciding roughly with the
terrestrial pole, and only show a slight increase, as
compared with other stars, as the galaxy is
approached." 1

Prof. Kapteyn thinks that " undoubtedly one
of the greatest difficulties, if not the greatest of
all, in the way of obtaining an understanding of
the real distribution of the stars in space, lies in
our uncertainty about the amount of loss suffered
by the light of the stars on its way to the
observer." 2 He says, " There can be little doubt
in my opinion, about the existence of absorption
in space, and I think that even a good guess as to
the order of its amount can be made. For, first

1 Howard Payn, Nature, May 1C, 1901, p. 56.

2 Contribution* from the Mount Wilwn Solar Olserratc.ry, No. 33.

322 ASTRONOMICAL CURIOSITIES

we know that space contains an enormous mass
of meteoric matter. This matter must necessarily
intercept some part of the star-light."

This absorption, however, seems to be compara-
tively small. Kapteyn finds a value of 0*016 (about
^th) of a magnitude for a star at a distance
corresponding to a parallax of one-tenth of a
second (about 33 " light years "). This is a quantity
almost imperceptible in the most delicate photo-
meter. But for very great distances — such as 3000
" light years " — the absorption would evidently
become very considerable, and would account
satisfactorily for the gradual " thinning out " of
the fainter stars. If this were fully proved, we
should have to consider the fainter stars of the
Milky Way to be in all probability fairly large
suns, the light of which is reduced by absorption.

That some of the ancients knew that the Milky
Way is composed of stars is shown by the
following lines translated from Ovid : —

" A way there is in heaven's extended plain
Which when the skies are clear is seen below
And mortals, by the name of Milky, know ;
The groundwork is of stars, through which the road
Lies open to great Jupiter's abode." 1

From an examination of the distribution of the
faint stars composing the Milky Way, and those
shown in Argelander's charts of stars down to the

1 Quoted by Denning in Telescopic Work for Starlight Evenings,
p. 297.

THE VISIBLE UNIVERSE 325

9J magnitude, Easton finds that there is "a real
connection between the distribution of 9th and
10 th magnitude stars, and that of the faint stars
of the Milky Way, and that consequently the
faint or very faint stars of the galactic zone are
at a distance which does not greatly exceed that
of the 9th and 10th magnitude stars." 1 A similar
conclusion was, I think, arrived at by Proctor
many years ago. Now let us consider the mean-
ing of this result. Taking stars of the 15th
magnitude, if their faiiitiiess were merely due to
greater distance, their actual brightness — if of
the same size — would imply that they are at 10
times the distance of stars of the 10th magnitude.
But if at the same distance from us, a 10th
magnitude star would be 100 times brighter than
a 15th magnitude star, and if of the same density
and " intrinsic brightness " (or luminosity of sur-
face) the 10th magnitude w^ould have 10 times
the diameter of the fainter star, and hence its
volume would be 1000 times greater (103), and this
great difference is not perhaps improbable.

The constitution of the Milky Way is not the
same in all its parts. The bright spot between
ft and y Cygiii is due to relatively bright stars.
Others equally dense but fainter regions in Auriga
and Monoceros are only evident in stars of the
8th and 9th magnitude, and the light of the well-
known luminous spot in "Sobieski's Shield,"
1 Astrophysical Journal, March, 1895.

ASTRONOMICAL CURIOSITIES

closely south of X Aquike, is due to stars below
magnitude 9J.

The correspondence in distribution between the
stars of Argelander's charts and the fainter stars
of the Milky Way shows, as Easton points out,
that Herschel's hypothesis of a uniform distribu-
tion of stars of approximately equal size is quite
untenable.

It has been suggested that the Milky Way may
perhaps form a ring of stars with the sun placed
nearly, but not exactly, in the centre of the ring.
But were it really a ring of uniform width with
the sun eccentrically placed within it, we should
expect to find the Milky Way wider at its nearest
part, and gradually narrowing towards the oppo-
site point. Now, Herschel's " gages " and Celoria's
counts show that the Galaxy is wider in Aquila
than in Monoceros. This is confirmed by Easton,
who says, "for the faint stars taken as a ivhole,
the Milky Way is widest in its brightest part"
(the italics are Easton' s). From this we should
conclude that the Milky Way is nearer to us in
the direction of Aquila than in that of Monoceros.
Sir John Herschel suggested that the southern
parts of the galactic zone are nearer to us on
account of their greater brightness in those
regions.1 But greater width is a safer test of
distance than relative brightness. For it may be
easily shown than the intrinsic brightness of an
1 Outlines of Astronomy, Tenth Edition, p. 571.

THE VISIBLE UNIVERSE 325

area containing a large number of stars would be
the same for all distances (neglecting the sup-
posed absorption of light in space). For suppose
any given area crowded with stars to be removed
to a greater distance. The light of each star
would be diminished inversely as the square of
the distance. But the given area would also be
diminished directly as the square of the distance,
so we should have a diminished amount of light
on an equally diminished area, and hence the
intrinsic brightness, or luminosity of the area per
unit of surface, would remain unaltered. The
increased brightness of the Milky Way in Aquila
is accounted for by the fact that Herschel's
" gages " show an increased number of stars, and
hence the brightness in Aquila and Sagittarius
does not necessarily imply that the Milky Way is
nearer to us in those parts, but that it is richer in
small stars than in other regions.

Easton is of opinion that the annular hypothesis
of the Milky Way is inconsistent with our present
knowledge of the galactic phenomena, and he
suggests that its actual constitution resembles
more that of a spiral nebula.1 On this hypothesis
the increase in the number of stars in the regions
above referred to may be due to our seeing one
branch of the supposed "two-branched spiral"
projected on another branch of the same spiral.
This seems supported by Sir John Herschel's
1 Astrophyaical Journal, vol. 12, p. 13G.

326 ASTRONOMICAL CURIOSITIES

observations in the southern hemisphere, where
he found in some places " a tissue as it were of
large stars spread over another of very small
ones, the immediate magnitudes being wanting."
Again, portions of the spiral branches may be
richer than others, as photographs of spiral
nebulae seem to indicate. Celoria, rejecting the
hypothesis of a single ring, suggests the existence
of two galactic rings inclined to each other at an
angle of about 20°, one of these including the
brighter stars, and the other the fainter. But
this seems to be a more artificial arrangement
then the hypothesis of a spiral. Further, the
complicated structure of the Milky Way cannot
be well explained by Celoria' s hypothesis of two
distinct rings one inside the other. From analogy
the spiral hypothesis seems much more probable.

Considering the Milky Way to represent a
colossal spiral nebula viewed from a point not
far removed from the centre of the spiral
branches, Easton suggests that the bright region
between /? and y Cygni, which is very rich in
comparatively bright stars, may possibly repre-
sent the " central accumulations of the Milky
Way," that is, the portion corresponding to the
nucleus of a spiral nebula. If this be so, this
portion of the Milky Way should be nearer to us
than others. Easton also thinks that the so-
called "solar cluster" of Gould, Kapteyn, and
Schiaparelli may perhaps be " the expression of

THE VISIBLE UNIVERSE

the central condensation of the galactic system
itself, composed of the most part of suns com-
parable with our own, and which would thus
embrace most of the bright stars to the 9th or
10th magnitude. The distance of the galactic
streams and convolutions would thus be com-
parable with the distances of these stars." He
thinks that the sun lies within a gigantic spiral,
"in a comparatively sparse region between the
central nucleus and Orion."

Scheiner thinks that "the irregularities of the
Milky Way, especially in streams, can be quite
well accounted for, as Easton has attempted to
do, if they are regarded as a system of spirals,
and not as a ring system."

Evidence in favour of the spiral hypothesis of
the Milky Way, as advocated by Easton and
Scheiner, may be found in Kapteyn's researches
on the proper motions of the stars. This eminent
astronomer finds that stars with measurable
proper motions — and therefore in all probability
relatively near the earth — have mostly spectra of
the solar type, and seem to cluster round " a point
adjacent to the sun, in total disregard to the
position of the Milky Way," and that stars with
little or no proper motion collect round the
galactic plain. He is also of opinion that the
Milky Way resembles the Andromeda nebula,
"the globular nucleus representing the solar
cluster, and the far spreading wings or whorls the

328 ASTRONOMICAL CURIOSITIES

compressed layer of stars enclosed by the rings of
the remote Galaxy."

With reference to the plurality of inhabited
worlds, it has been well said by the ancient writer
Metrodorus (third century B.C.), "The idea that
there is but a single world in all infinitude would be
as absurd as to suppose that a vast field had been
formed to produce a single blade of wheat." l With
this opinion the present writer fully concurs.

1 De Placitis. Quoted by Carl Snyder in The World Machine
p, 354.

CHAPTER XXI

General

THE achievements of Hipparchus in
astronomy were very remarkable, con-
sidering the age in which he lived. He
found the amount of the apparent motion of the
stars due to the precession of the equinoxes (of
which he was the discoverer) to be 59" per
annum. The correct amount is about 50". He
measured the length of the year to within 9
minutes of its true value. He found the inclina-
tion of the ecliptic to the plane of the equator to
be 23° 51'. It was then 23° 46'— as we now know
by modern calculations — so that Hipparchus'
estimation was a wonderfully close approxima-
tion to the truth. He computed the moon's
parallax to be 57', which is about its correct value.
He found the eccentricity of the sun's apparent
orbit round the earth to be one twenty -fourth, the
real value being then about one-thirteenth. He
determined other motions connected with the
earth and moon ; and formed a catalogue of 1080
stars. All this work has earned for him the
Avell-merited title of " The Father of Astronomy." l
1 Popular Astronnmy, vol. 14 (1906), p. 638.

330 ASTRONOMICAL CURIOSITIES

The following is a translation of a Greek passage
ascribed to Plotemy : " I know that I am mortal
and the creature of a day, but when I search out
the many rolling circles of the stars, my feet
touch the earth no longer, but with Zeus himself
I take my fill of ambrosia, the food of the gods." l
This was inscribed (in Greek) on a silver loving
cup presented to the late Professor C. A. Young,
the famous American astronomer.2

Some curious and interesting phenomena are
recorded in the old Chinese Annals, which go
back to a great antiquity. In 687 B.C. " a night "
is mentioned "without clouds and without
stars " (!) This may perhaps refer to a total
eclipse of the sun ; but if so, the eclipse is not
mentioned in the Chinese list of eclipses. In the
year 141 B.C., it is stated that the sun and moon
appeared of a deep red colour during 5 days, a
phenomenon which caused great terror among the
people. In 74 B.C., it is related that a star as
large as the moon appeared, and was followed in
its motion by several stars of ordinary size. This
probably refers to an unusually large " bolide *'
or " fireball." In 38 B.C., a fall of meteoric stones
is recorded " of the size of a walnut." In A.D. 88,
another fall of stones is mentioned. In A.D. 321,
sun-spots were visible to the naked eye.

1 Article on " The Greek Anthology," Nineteenth Century, April,
1907, quoted in The Observatory, May, 1907.

2 Popular Astronomy, vol. 13 (1905), p. 34G.

GENERAL 331

Homer speaks of a curious darkness which
occurred during one of the great battles in the
last year of the Trojan war. Mr. Stock well
identifies this with an eclipse of the sun which
took place on August 28, 1184 B.C. An eclipse
referred to by Thucydides as having occurred dur-
ing the first year of the Pelopomiesiaii War, when
the darkness was so great that some stars were
seen, is identified by Stockwell with a total eclipse
of the sun, which took place on August 2, 430 B.C.

A great eclipse of the sun is supposed to have
occurred in the 'year 43 or 44 B.C., soon after the
death of Julius Caesar. Baron de Zach and Arago
mention it as the first annular eclipse on record.
But calculations show that no solar eclipse what-
ever, visible in Italy, occurred in either of these
years. The phenomenon referred to must there-
fore have been of atmospherical origin, and indeed
this is suggested by a passage in Suetonius, one
of the authors quoted on the subject.

M. Guillaurne thinks that the ninth Egyptian

plague, the thick "darkness" (Exodus x. 21-23),

may perhaps be explained by a total eclipse

of the sun which occurred in 1332 B.C. It is

true that the account states that the darkness

lasted " three days," but this, M. Guillaume thinks,

may be due to an error in the translation.1 This

explanation, however, seems very improbable.

According to Hind, the moon was eclipsed on

1 Bulletin de la Soc. Ast. de France, April, 1908.

332 ASTRONOMICAL CURIOSITIES

the generally received date of the Crucifixion,
A.D. 33, April 3. He says, " I find she had
emerged from the earth's dark shadow a quarter
of an hour before she rose at Jerusalem
(6h 36m p.m.) ; but the penumbra continued upon
her disc for an hour afterwards." An eclipse
could not have had anything to do with the
"darkness over all the land" during the Cruci-
fixion. For this lasted for three hours, and the
totality of a solar eclipse can only last a few
minutes at the most. As a matter of fact the
" eclipse of Phlegon," a partial one (A.D. 29,
November 24) was " the only solar eclipse that
could have been visible in Jerusalem during
the period usually fixed for the ministry of
Christ."

It is mentioned in the Anglo-Saxon Chronicle
that a total eclipse of the sun took place in the
year after King Alfred's great battle with the
Danes. Now, calculation shows that this
eclipse occurred on October 29, 878 A.D. King
Alfred's victory over the Danes must, therefore,
have taken place in 877 A.D., and his death pro-
bably occurred in 899 A.D. This solar eclipse is
also mentioned in the Annals of Ulster. From
this it will be seen that in some cases the dates of
historical events can be accurately fixed by
astronomical phenomena.

It is stated by some historians that an eclipse of
the sun took place on the morning of the battle of

GENERAL 333

Crecy, August 26, 1346. But calculation shows
that there was no eclipse of the sun visible in
England in that year. At the time of the famous
battle the moon had just entered on her first
quarter, and she was partially eclipsed six days
afterwards — that is on the 1st of September. The
mistake seems to have arisen from a mistrans-
lation of the old French word esclistre, which
means lightning. This was mistaken for esclipse.
The account seems to indicate that there was a
heavy thunderstorm on the morning of the
battle.

A dark shade was seen on the waning moon by
Messrs. Hirst and J. C. Russell on October 21, 1878,
" as dark as the shadow during an eclipse of the
moon."1 If this observation is correct, it is
certainly most difficult to explain. Another
curious observation is recorded by Mr. E. Stone
Wiggins, who says that a partial eclipse of the
sun by a dark body was observed in the State of
Michigan (U.S.A.) on May 16, 1884, at 7 p.m. The
" moon at that moment was 12 degrees south of
the equator and the sun as many degrees north
of it." The existence of a dark satellite of the
earth has been suggested, but this seems highly
improbable.

The sun's corona seems to have been first
noticed in the total eclipse of the sun which
occurred at the death of the Roman emperor
1 The Observatory, vol. 11, p. 375,

ASTRONOMICAL CURIOSITIES

Doniitian, A.D. 95. Philostratus in his Life of
Apollonius says, with reference to this eclipse,
" In the heavens there appeared a prodigy of this
nature : a certain corona resembling the Iris
surrounded the orb of the sun, and obscured its
light." * In more modern times the corona seems
to have been first noticed by Clavius during the
total eclipse of April 9, 1567. 2 Kepler proved that
this eclipse was total, not annular, so that the
ring seen by Clavius must have been the corona.

With reference to the visibility of planets and
stars during total eclipses of the sun ; in the
eclipse of May 12, 1706, Venus, Mercury, and
Aldebaran, and several other stars were seen.
During the totality of the eclipse of May 3, 1715,
about twenty stars were seen with the naked eye. '
At the eclipse of May 22, 1724, Venus and Mercury,
and a few fixed stars were seen.4 The corona was
also noticed. At the eclipse of May 2, 1733,
Jupiter, the stars of the " Plough," Capella, and
other stars were visible to the naked eye ; and the
corona was again seen.4

During the total eclipses of February 9, 17G6,
June 24, 1778, and June 16, 1806, the corona was
again noticed. But its true character was then
unknown.

At the eclipse of July 8, 1842, it was noticed by

1 Grant, History of Physical Astronomy, p, 364.

2 Ibid., p. 377. 3 11>id.t p. 366.
4 lliil, p. 307.

GENERAL 335

observers at Lipesk that the stars Aldebaran and
Betelgeuse (a Orionis), which are usually red.
*' appeared quite white." 1

There will be seven eclipses in the years 1917,
1935, and 1985. In the year 1935 there will be five
eclipses of the sun, a rare event ; and in 1985
there will be three total eclipses of the moon, a
most unusual occurrence.2

Among the ancient Hindoos, the common people
believed that eclipses were caused by the inter-
position of a monstrous demon called Raha. This
absurd idea, and others equally ridiculous, were
based on declarations in their sacred books, and
no pious Hindoo would think of denying it.

The following cases of darkenings of the sun are
given by Humboldt : —

According to Plutarch the sun remained pale for
a whole year at the death of Julius Caesar, and
gave less than its usual heat.3

A sun-darkening lasting for two hours is re-
corded on August 22, 358 A.D., before the great
earthquake of Nicomedia.

In 360 A.D. there was a sun-darkening from early
morn till noon. The description given by the
historians of the time corresponds to an eclipse
of the sun, but the duration of the obscurity is
inexplicable.

In 409 A.D., when Alaric lay siege to Rome,

1 Grant, History of Physical Astronomy, p. 370.
2 Nature, July 25, 1889. 3 Cosmos, vol. iv. p. 381.

336 ASTRONOMICAL CURIOSITIES

"there was so great a darkness that the stars
were seen by day."

In 536 A.D. the sun is said to have been darkened
for a year and two months !

In 626 A.D., according to Abul Farag, half the
sun's disc was darkened for eight months !

In 934 A.D. the sun lost its brightness for two
months in Portugal.

In 1090 A.D. the sun was darkened for three
hours.

In 1096, sun-spots were seen with the naked eye
on March 3.

In 1206 A.D. on the last day of February, " there
was complete darkness for six hours, turning the
day into night." This seems to have occurred in
Spain.

In 1241 the sun was so darkened that stars
could be seen at 3 p.m. on Michaelmas day. This
happened in Vienna.1

The sun is said to have been so darkened in the
year 1547 A.D. for three days that stars were
visible at midday. This occurred about the time
of the battle of Miihlbergh.2

Some of these darkenings may possibly have
been due to an enormous development of sun-
spots ; but in some cases the darkness is supposed
by Chladni and Schnurrer to have been caused by
" the passage of meteoric masses before the sun's
disc."

1 Cosmos, vol. iv. pp, 881-6, 3 lUd.} vol. i, p. 121.

GENERAL 337

The first observer of a transit of Venus was
Jeremiah Horrocks, who observed the transit of
November 24 (O.S.), 1639. He had previously
corrected Kepler's predicted tune of the transit
from 8h 8m a.m. at Manchester to 5h 57m p.m. At
the end of 1875 a marble scroll was placed on the
pedestal of the monument of John Conduitt
(nephew of Sir Isaac Newton, and who adopted
Horrocks' theory of lunar motions) at the west
end of the nave of Westminster Abbey, bearing
this inscription from the pen of Dean Stanley —

f( Ad majora avocatus
quse ob ha?c parerga uegligi non decuit "

IN MEJIORY OF

JEREMIAH HORROCKS

Curate of Hoole in Lancashire

Who died on the 3d of January, 1641, in or near his

22d year

Having in so short a life
Detected the long inequality in the mean motion of

Jupiter and Saturn
Discovered the orbit of the Moon to be an ellipse ;

Determined the motion of the lunar aspe,
Suggested the physical cause of its revolution ;
And predicted from his own observations, the

Transit of Venus
Which was seen by himself and his friend

WILLIAM CRABTREE

\ On Sunday, the 24th November (O.S.) 1639 ;
This Tablet, facing the Monument of Newton
Was raised after the lapse of more than two centuries
December 9, 1874. l

» The Observatory, vol. 6 (1883), pp. 327-8.

338 ASTRONOMICAL CURIOSITIES

The transit of Venus which occurred in 1761
was observed on board ship(!) by the famous
but unfortunate French astronomer Le Gentil.
The ship was the frigate Sylphide, sent to the
help of Pondicherry (India) which was then being
besieged by the English. Owing to unfavourable
winds the Sylphide was tossed about from
March 25, 1761, to May 24 of the same year.
When, on the later date, off the coast of Malabar,
the captain of the frigate learned that Pondicherry
had been captured by the English, the vessel
returned to the Isle of France, where it arrived
on June 23, after touching at Point de Galle 011
May 30. It was between these two places that
Le Gentil made his observations of the transit
of Venus under such unfavourable conditions.
He had an object-glass of 15 feet (French) focus,
and this he mounted in a tube formed of " four
pine planks." This rough instrument was fixed
to a small mast set up on the quarter-deck and
worked by ropes. The observations made under
such curious conditions, were not, as may be
imagined, very satisfactory. As another transit
was to take place 011 June 3, 1769, Le Gentil made
the heroic resolution of remaining in the southern
hemisphere to observe it! This determination
was duly carried out, but his devotion to astronomy
was not rewarded ; for on the day of the long
waited for transit the sky at Pondicherry (where
he had gone to observe it) was clouded over

GENERAL 339

during the whole phenomenon, " although for
many days previous the sky had been cloudless.'*
To add to his feeling of disappointment he heard
that at Manilla, where he had been staying some
time previously, the sky was quite clear, and two
of his friends there had seen the transit without
any difficulty.1 Truly the unfortunate Le Gentil
was a martyr to science.

The famous German astronomer Bessel once
said " that a practical astronomer could make
observations of value if he had only a cart-wheel
and a gun barrel " ; and Watson said that " the
most important part of the instrument is the
person at the small end." 2

With reference to Father Hell's supposed
forgery of his observations of the transit of
Venus in 1769, and Littrow's criticism of some of
the entries in Hell's manuscript being corrected
with a different coloured ink, Professor Newcomb
ascertained from Weiss that Littrow was colour
blind, and could not distinguish between the
colour of Aldebaran and the whitest star." New-
comb adds, " For half a century the astronomical
world had based an impression on the innocent
but mistaken evidence of a colour-blind man
respecting the tint of ink in a manuscript."

It is recorded that on February 26, B.C. 2012,
the moon, Mercury, Venus, Jupiter, and Saturn,

1 Nature, June 25, 1874.

2 Popular Astronomy, May, 1895, " Reflectors or Refractors."

340 ASTRONOMICAL CURIOSITIES

were in the same constellation, and within 14
degrees of each other. On September 14, 1186 A.D.,
the sun, moon, and all the planets then known,
are said to have been situated in Libra.1

In the Sanscrit epic poem, " The Ramaya," it is
stated that at the birth of Rama, the moon was
in Cancer, the sun in Aries, Mercury in Taurus,
Venus in Pisces, Mars in Capricornus, Jupiter in
Cancer, and Saturn in Libra. From these data,
Mr. Walter R. Old has computed that Rama was
born on February 10, 1761 B.C.2

A close conjunction of Mars and Saturn was
observed by Denning on September 29, 1889, the
bright star Regulus (a Leonis) being at the time
only 47' distant from the planets.3

An occultation of the Pleiades by the moon
was observed by Timocharis at Alexandria on
January 29, 282 B.C. Calculations by Schjellerup
show that Alcyone (>; Tauri) was occulted; but
the exact time of the day recorded by Timocharis
differs very considerably from that computed
by Schjellerup.4 Another occultation of the
Pleiades is recorded by Agrippa in the reign of
Domitian. According to Schjellerup the pheno-
menon occurred on November 29, A.D. 92.

" Kepler states that on the 9th of January, 1591,

1 Denning, Telescopic Work for Starlight Evenings, p. 225.

2 Nature, November 2, 1893.

3 Telescopic Work, p. 226.

' 4 Copernicus, vol. i. p. 229.

GENERAL

Maestlin and himself witnessed an occultation of
Jupiter by Mars. The red colour of the latter on
that occasion plainly indicated that it was the
inferior planet." l That is, that Mars was nearer
to the sun than Jupiter. But as the telescope
had not then been invented, this may have been
merely a near approach of the two planets.

According to Kepler, Msestlin. saw an occultation
of Mars by Venus on October 3, 1590. But this
may also have been merely a near approach.1

A curious paradox is that one can discover an
object without seeing it, and see an object without
discovering it ! The planet Neptune was dis-
covered by Adams and Leverrier by calculation
before it was seen in the telescope by Galle ; and
it was actually seen by Lalande on May 8 and 10,
1795, but he took it for a star and thus missed the
discovery. In fact, he saiv the planet, but did not
discover it. It actually appears as a star of the
8th magnitude in Harding's Atlas (1822). The
great " new star " of February, 1901, known as
Nova Persei, was probably seen by some people
before its discovery was announced ; and it was
actually noticed by a well-known American
astronomer, who thought it was some bright star
with which he was not familiar! But this did
not amount to a discovery. Any one absolutely
ignorant of astronomy might have made the same
observation. An object must be identified as a
1 Grant, History of Physical Astronomy^ p. 433,

ASTRONOMICAL CURIOSITIES

new object before a discovery can be claimed.
Some years ago a well-known Irish naturalist
discovered a spider new to science, and after its
discovery he found that it was common in nearly
every house in Dublin ! But this fact did not
detract in the least from the merit of its scientific
discovery.

There is a story of an eminent astronomer who
had been on several eclipse expeditions, and yet
was heard to remark that he had never seen a
total eclipse of the sun. " But your observations
of several eclipses are on record," it was objected.
" Certainly, I have on several occasions made
observations, but I have always been too busy to
look at the eclipse." He was probably in a dark
tent taking photographs or using a spectroscope
during the totality. This was observing an
eclipse without seeing it !

Humboldt gives the credit of the invention of
the telescope to Hans Lippershey, a native of
Wesel and a spectacle-maker at Middleburgh ; to
Jacob Adreaansz, surnamed Metius, who is also
said to have made burning-glasses of ice ; and to
Zachariah Jansen.1

With reference to the parabolic figure of the
large mirrors of reflecting telescopes, Dr. Robinson
remarked at the meeting of the British Associa-
tion at Cork in 1843, " between the spherical and
parabolic figures the extreme difference is so
1 Cosmos, vol. ii. p. 099.

GENERAL 343

slight, even in the telescope of 6-feet aperture
[Lord Rosse's] that if the two surfaces touched
at their vertex, the distance at the edge would
not amount to the foiooth °^ an inch, a space
which few can measure, and none without a
microscope." 1

In the year 1758, Roger Long, Lowndean Pro-
fessor of Astronomy at Cambridge, constructed an
"orrery" on a novel principle. It was a hollow
metal sphere of about 18 feet in diameter with
its fixed axis parallel to the earth's axis. It was
rotated, by means of a winch and rackwork. It
held about thirty persons in its interior, where
astronomical lectures were delivered. The con-
stellations were painted 011 the interior surface;
and holes pierced through the shell and illumi-
nated from the outside represented the stars
according to their different magnitudes. This
ingenious machine was much neglected for many
years, but was still in existence in Admiral
Smyth's time, 1844.2

A " temporary star " is said to have been seen
by Hepidanus in the constellation Aries in either
1006 or 1012 A.D. The late M. Schonfeld, a great
authority 011 variable stars, found from an Arabic
and Syrian chronicle that 1012 is the correct year
(396 of the Hegira), but that the word translated
Aries would by a probable emendation mean

1 Grant, History of Physical Astronomy, p. 536, footnote.

2 Bedford Catalogue, p. 179.

344 ASTRONOMICAL CURIOSITIES

Scorpio. The word in the Syrian record is not
the word for Aries.1

Mr. Heber D. Curtis finds that the faintest stars
mentioned in Ptolemy's Catalogue are about 5*38
magnitude on the scale of the Harvard Photo-
metric Durchmustering.2 Heis and Houzeaii saw
stars of 6-7 magnitude (about 6'4 on Harvard
scale). The present writer found that he could
see most of Heis' faintest stars in the west of
Ireland (Co. Sligo) without optical aid (except
short-sighted spectacles).

With reference to the apparent changes in the
stellar heavens produced by the precession of the
equinoxes, Humboldt says —

" Canopus was fully 1° 20' below the horizon
of Toledo (39° 54' north latitude) in the time of
Columbus ; and now the same star is almost as
much above the horizon of Cadiz. While at
Berlin, and in northern latitudes, the stars of the
Southern Cross, as well as a and fi Centauri, are
receding more and more from view, the Magellamc
Clouds are slowly approaching our latitudes.
Canopus was at its greatest northern approxi-
mation during last century [eighteenth], and is
now moving nearer and nearer to the south,
although very slowly, owing to its vicinity to the
south pole of the ecliptic. The Southern Cross
began to become invisible in 52° 30' north latitude
2900 years before our era, since, according to
Galle, this constellation might previously have
reached an altitude of more than 10°. When it

1 The Observatory, July, 1891.

2 Nature, September 3, 1903.

GENERAL 345

had disappeared from the horizon of the countries
of the Baltic, the great pyramid of Cheops had
already been erected more than five hundred
years. The pastoral tribe of the Hyksos made
their incursion seven hundred years earlier. The
past seems to be visibly nearer to us when we
connect its measurement with great and memor-
able events." l

With reference to the great Grecian philosopher
and scientist Eratosthenes of Cyrene, keeper of
the Alexandrian Library under Ptolemy Euergetes,
Carl Snyder says, " Above all the Alexanders,
Caesars, Tadema-Napoleons, I set the brain which
first spanned the earth, over whose little patches
these fought through their empty bootless lives.
Why should we have no poet to celebrate so great
a deed ? " 2 And with reference to Aristarchus he
says, "If grandeur of conceptions be a measure
of the brain, or ingenuity of its powers, then we
must rank Aristarchus as one of the three or four
most acute intellects of the ancient world." 3

Lagrange, who often asserted Newton, to be the
greatest genius that ever existed, used to remark
also — " and the most fortunate ; we do not
find more than once a system of the world to
establish." 4

Grant says —

" Lagrange deserves to be ranked among the

1 Cosmos, vol. ii. p. 6G9.

2 The World Machine, p. 80. 3 Ibid., p, 89,
4 Grant, History of Physical Astronomy, p. 107.

346 ASTRONOMICAL CURIOSITIES

greatest mathematical geniuses of ancient or
modern times. In this respect he is worthy of
a place with Archimedes or Newton, although
he was far from possessing the sagacity in
physical enquiries which distinguished these
illustrious sages. From the very outset of his
career he assumed a commanding position among
the mathematicians of the age, and during the
course of nearly half a century previous to his
death, he continued to divide with Laplace the
homage due to pre-eminence in the exact sciences.
His great rival survived him fourteen years,
during which he reigned alone as the prince of
mathematicians and theoretical astonomers." x

A writer in Nature (May 25, 1871) relates the
following anecdote with reference to Sir John
Herschel : " Some time after the death of Laplace,
the writer of this notice, while travelling on the
continent in company with the celebrated French
savant Biot, ventured to put to him the question,
not altogether a wise one, * And whom of all the
philosophers of Europe do you regard as the most
worthy successor of Laplace ? ' Probably no man
was better able than Biot to form a correct con-
clusion, and the reply was more judicious than
the question. It was this, « If I did not love him
so much I should unhesitatingly say, Sir John
Herschel.' " Dr. Gill (now Sir David Gill), in an
address at the Cape of Good Hope in June, 1898,
spoke of Sir John Herschel as " the prose poet of
science ; his popular scientific works are models of

1 Grant, History of Physical Astronomy, ]-. 113.

GENERAL 347

clearness, and his presidential addresses teem with
passages of surpassing beauty. His life was a
pure and blameless one from first to last, full
of the noblest effort and the noblest aim from
the time when as a young Cambridge graduate he
registered a vow * to try to leave the world wiser
than he found it' — a vow that his life amply
fulfilled." x

Prof. Newcomb said of Adams, the co-discoverer
of Neptune with Leverrier, "Adams' intellect
was one of the keenest I ever knew. The most
difficult problem of mathematical astronomy
and the most recondite principles that underlie
the theory of the celestial motions were to him
but child's play." Airy he regarded as "the most
commanding figure in the astronomy of our
time." 2 He spoke of Delaunay, the great French
astronomer, as a most kindly and attractive man,
and says, "His investigations of the moon's
motion is one of the most extraordinary pieces of
mathematical work ever turned out by a single
person. It fills two quarto volumes, and the
reader who attempts to go through any part of
the calculations will wonder how one man could
do the work in a lifetime." 3

Sir George B. Airy and Prof. J. C. Adams died
in the same month. The former on January 2,

1 Nature, August 11, 1898.

2 Jbid., August 18, 1898.

3 JIM., October 20, 1898.

348 ASTRONOMICAL CURIOSITIES

1892, and the latter on January 22 of the same
year.

It is known from the parish register of Burstow
in Surrey that Flamsteed (Rev. John Flamsteed),
the first Astronomer Royal at Greenwich, was
buried in the church at that place on January 12,
1720 ; but a search for his grave made by Mr. J.
Carpenter in 1866 and by Mr. Lynn in 1880 led to
no result. In Mrs. Flamsteed's will a sum of
twenty-five pounds was left for the purpose of
erecting a monument to the memory of the great
astronomer in Burstow Church; but it does not
appear that any monument was ever erected.
Flamsteed was Rector of the Parish of Burstow.1
He was succeeded in 1720 by the Rev. James
Pound, another well-known astronomer. Pound
died in 1724.2

Evelyn says in his Diary, 1676, September 10,
" Dined with Mr. Flamsteed, the learned astrologer
and mathematician, whom his Majesty had
established in the new Observatory in Greenwich
Park furnished with the choicest instruments.
An honest sincere man." 3 This shows that in
those days the term " astrologer " was synonymous
with " astronomer."

In an article on "Our Debt to Astronomy,"
by Prof. Russell Tracy Crawford (Berkeley

1 The Observatory, vol. iv. (1881), p. 234.

2 W. T. Lynn, The Observatory, July, 1909, p. 291.
8 Quoted in The Observatory, July, 1902, p, 281,

GENERAL 349

Astronomical Department, California, U.S.A.), the
following remarks occur : —

"Behind the artisan is a chemist, behind the
chemist is a physicist, behind the physicist is
a mathematician, and behind the mathematician
is an astronomer." "Were it not for the data
furnished by astronomers, commerce by sea
would practically stop. The sailing-master on
the high seas could not determine his position,
nor in what direction to head his ship in order
to reach a desired harbour. Think what this
means in dollars and cents, and estimate it if
you can. For this one service alone the science
of astronomy is worth more in dollars and cents
to the world in one week than has been expended
upon it since the beginning of civilization. Do
you think that Great Britain, for instance, would
take in exchange an amount equal to its national
debt for what astronomy gives it ? I answer for
you most emphatically, ' No.' "

In his interesting book, Reminiscences of an
Astronomer, Prof. Simon Newcomb says with
reference to the calculations for the Nautical
Almanac (referred to in the above extract) —

" A more hopeless problem than this could not be
presented to the ordinary human intellect. There
are tens of thousands of men who could be
successful in all the ordinary walks of life,
hundreds who could wield empires, thousands
who could gain wealth, for one who could take
up this astronomical problem with any hope of
success. The men who have done it are, therefore,
in intellect the select few of the human race — an
aristocracy ranking above all others in the scale
of being. The astronomical ephemeris is the last
outcome of their productive genius."

350 ASTRONOMICAL CURIOSITIES

In a paper on the " Aspects of American
Astronomy," Prof. Newcomb says, " A great tele-
scope is of no use without a man at the end of it,
and what the telescope may do depends more
upon this appendage than upon the instrument
itself. The place which telescopes and observa-
tories have taken in astronomical history are by
no means proportional to their dimensions. Many
a great instrument has been a mere toy in the
hands of its owner. Many a small one has
become famous. Twenty years ago there was
here in your city [Chicago] a modest little instru-
ment which, judged by its size, could not hold
up its head with the great ones even of that day.
It was the private property of a young man
holding no scientific position and scarcely known
to the public. And yet that little telescope is
to-day among the famous ones of the world, having
made memorable advances in the astronomy of
double stars, and shown its owner to be a worthy
successor of the Herschels and Struves in that
line of work." 1 Here Prof. Newcomb evidently
refers to Prof. Burnham, and the 6-inch telescope
with which he made many of his remarkable
discoveries of double stars. With reference to
Burnham's work, Prof. Barnard says —

" It represents the labour of a struggling
amateur, who during the day led the drudging
life of a stenographer in the United States court

1 Astrophysical Journal, vol. 6, 1897, p. 804.

GENERAL 351

in Chicago, and at night worked among the stars
for the pure love of it. Such work deserves an
everlasting fame, and surely this has fallen to Mr
Buriiham."

Admiral Smyth says —

" A man may prove a good astronomer without
possessing a spacious observatory : thus Kepler
was wont to observe on the bridge at Prague ;
Schroter studied the moon, and Harding found
a planet from a gloriette ; while Olbers discovered
two new planets from an attic of his house." x

It is probably not generally known that " some
of the greatest astronomers of modern times, such
as Kepler, Newton, Hansen, Laplace, and Leverrier,
scarcely ever looked through a telescope." 2

Kepler, who always signed himself Keppler in
German, is usually supposed to have been born
on December 21, 1571, in the imperial town of
Weil, but according to Baron von Breitschwert,3
he was really born on December 27, 1571, in the
village of Magstadt in Wurtemberg.

According to Lieut. Winterhalter, M. Perrotin
of the Nice Observatory declared " that two hours'
work with a large instrument is as fatiguing as
eight with a small one, the labour involved in-
creasing in proportion to the cube of the aperture,
the chances of seeing decreasing in the same ratio,

1 Celestial Cycle, p. 367.

2 The Observatory, vol. 5 (1882), p. 251.

3 Quoted by Humboldt in Cosmos, vol. ii. p. 696, footnote.

352 ASTRONOMICAL CURIOSITIES

while it can hardly be said that the advantages
increase in like proportion." l
The late Mr. Proctor has well said —

" It is well to remember that the hatred which
many entertain against the doctrine of develop-
ment as applied to solar systems and stellar
galaxies is not in reality a sign, as they imagine,
of humility, but is an effort to avoid the recog-
nition of the nothingness of man in the presence
of the infinities of space and time and vitality
presented within the universe of God." 2

Humboldt says —

"That arrogant spirit of incredulity, which
rejects facts without attempting to investigate
them, is , in some cases almost more injurious
than an unquestioning credulity. Both are alike
detrimental to the force of investigations." 3

With reference to the precession of the
equinoxes and the changes it produces in the
position of the Pole Star, it is stated in a recent
book on science that the entrance passage of
the Great Pyramid of Ghizeh is inclined at an
angle of 30° to the horizon, and therefore points to
the celestial pole. But this is quite incorrect.
The Great Pyramid, it is true, is situated close to
the latitude of 30°. But the entrance passage
does not point exactly to the pole. The inclina-
tion was measured by Col. Vyse, and found to be

1 Quoted by Denning in Telescopic Work, p. 347.

2 Knowledge, February 20, 1885, p. 149.

3 Humboldt's Cosmos, vol. i. p. 123,

GENERAL 353

26° 45'. For six out of the nine pyramids of Gliizeh,
Col. Vyse found an average inclination ~of 26° 47',
these inclinations ranging from 25° 55' (2nd, or
pyramid of Mycerinus) to 28° 0' (9th pyramid).1
Sir John Herschel gives 3970 B.C. as the probable
date of the erection of the Great Pyramid.1 At
that time the distance of a Draconis (the Pole Star
of that day) from the pole was 3° 44' 25", so that
when on the meridian beloiv the pole (its lower
culmination as it is termed) its altitude was
30° - 3° 44' 25" = 26° 15' 35", which agrees fairly
well with the inclination of the entrance passage.
Letronne found a date of 3430 B.C. ; but the earlier
date agrees better with the evidence derived from
Egyptology.
Emerson says —

" I sin brother to him who squared the pyramids
By the same stars I watch."

' From February 6 to 15, 1908, all the bright
planets were visible together at the same time.
Mercury was visible above the western horizon
after sunset, Venus very brilliant with Saturn a
little above it, Mars higher still, all ranged along
the ecliptic, and lastly Jupiter rising in the east.2
This simultaneous visibility of all the bright
planets is rather a rare occurrence.

"With reference to the great improbability of

1 Outlines of Astronomy, par. 319 ; edition of 1875.

- Bulletin de la Soc. Ast. de France, March, 1908, p. 146.

2 A

354 ASTRONOMICAL CURIOSITIES

Laplace's original Nebular Hypothesis being true,
Dr. See says, " We may calculate from the pre-
ponderance of small bodies actually found in the
solar system — eight principal planets, twenty-five
satellites (besides our moon), and 625 asteroids —
that the chances of a nebula devoid of hydrostatic
pressure producing small bodies is about 2s58 to 1,
or a decillion decillion (1066)6 to the sixth power,
to unity. This figure is so very large that we
shall content ourselves with illustrating a decillion
decillion, and for this purpose we avail ourselves
of a method employed by ARCHIMEDES to illus-
trate his system of enumeration. Imagine sand
so fine that 10,000 grains will be contained in
the space occupied by a poppy seed, itself about
the size of a pin's head ; and then conceive a sphere
described about our sun with a radius of 200,000
astronomical units 1 (a Centauri being at a dis-
tance of 275,000) entirely filled with this fine sand.
The number of grains of sand in this sphere of
the fixed stars would be a decillion decillion2
(1066)6. All these grains of sand against one is the
probability that a nebula devoid of hydrostatical
pressure, such as that which formed the planets
and satellites, will lead to the genesis of such
small bodies revolving about a greatly predominant

1 An " astronomical unit " is the sun's mean distance from the
earth.

2 This is on the American and French system of notation,
but on the English system, 10«6 = 10"° X 106 would be a million
decillion.

GENERAL 355

central mass." l In other words, it is practically
certain that the solar system was not formed from
a gaseous nebula in the manner originally pro-
posed by Laplace. On the other hand, the evolu-
tion of the solar system from a rotating spiral
nebula seems very probable.

Some one has said that " the world knows
nothing of its greatest men." The name of Mr.
George W. Hill will probably be unknown to many
of my readers. But the late Prof. Simon Newcomb
said of him that he " will easily rank as the greatest
master of mathematical astronomy during the
last quarter of the nineteenth century." 2 Of
Prof. Newcomb himself — also a great master in
the same subject — Sir Robert Ball says he was
" the most conspicuous figure among the brilliant
band of contemporary American astronomers." 3

An astronomer is supposed to say, with reference
to unwelcome visitors to his observatory, "Who
steals my purse steals trash ; but he that filches
from me my clear nights, robs me of that which
not enriches him, and makes me poor indeed." 4

Cicero said, " In the heavens there is nothing
fortuitous, unadvised, inconstant, or variable ;
all there is order, truth, reason, and constancy " ;
and he adds, " The creation is as plain a signal

1 Astronomical Society of the Pacific, April, 1909 (No. 125), and
Popular Astronomy, May, 1909.

2 Nature, July 22, 1909. 3 Ibid.
4 The Observatory, vol. 9 (December, 188G), p. 389.

356 ASTRONOMICAL CURIOSITIES

of the being of a God, as a globe, a clock, or other
artificial machine, is of a man." l

"Of all the epigrams attributed rightly or
wrongly to Plato, the most famous has been
expanded by Shelley into the four glorious lines —

" * Thou wert the morning star among the living

Ere thy pure light had fled,
Now having died, thou art as Hesperus, giving
New splendour to the dead.' " 2

Sir David Brewster has well said,3 " Isaiah
furnishes us with a striking passage, in which the
occupants of the earth and the heavens are
separately described, * I have made the earth,
and created man upon it : I, even My hands, have
stretched out the heavens, and all their host have
I commanded' (Isaiah xlv. 12). But in addition
to these obvious references to life and things
pertaining to life, we find in Isaiah the following
remarkable passage : 4 For thus saith the Lord
that created the heavens ; God Himself that
formed the earth and made it ; He hath established
it, He created it not IN VAIN, He formed it to be
inhabited ' (Isaiah xlv. 18). Here we have a
distinct declaration from the inspired prophet
that the earth would have been created IN VAIN
if it had not been formed to be inhabited; and
hence we draw the conclusion that as the Creator
cannot be supposed to have made the worlds of

1 De Nat. JDeorwm, quoted in Smyth's Cycle, p. 19.

2 The Observatory, May, 1907.

3 More Worlds than Ours, p. 17.

GENERAL 357

our system and those in the sidereal system in
vain, they must have been formed to be inhabited."
This seems to the present writer to be a good and
sufficient reply to Dr. Wallace's theory that our
earth is the only inhabited world in the Universe ! *
Such a theory seems incredible.

The recent discovery made by Prof. Kapteyn,
and confirmed by Mr. Eddington, of two drifts
of stars, indicating the existence of two universes,
seems to render untenable Dr. Wallace's hypothesis
of the earth's central position in a single universe.1

1 Man's Place in Nature.

NOTE ADDED IN THE PRESS.

While these pages were in the Press, it was announced,
by Dr. Max Wolf of Heidelberg, that he found Halley's
comet on a photograph taken on the early morning of
September 12, 1909. The discovery has been confirmed at
Greenwich Observatory. The comet was close to the
position predicted by the calculations of Messrs. Cowell and
Crommelin of Greenwich Observatory (Nature, September 1C,
1908).

INDEX

Aboukir, 287

Aboul Hassan, 221

Abu All al Paris! , 225

Abu-Hanifa, 233, 234

Abul-fadl, 236

Ascadians, 250, 252

A;hernar, 275

Aclian, 282

Adam, 96, 347

Adhad-al-Davlat, 225, 236

Adonis, 261

Adreaansz, 342

Airy, Sir G. B., 87, 140, 347,
357

Aitken, 160

Al-Battani, 232, 233

Albrecht, 173

Albufaragius, 283

Alcor, 241

Alcyone, 137

Aldebaran, 60, 156, 236, 252,
257, 310, 311

Alfard, 236, 289

Alfargani, 286

Alfraganus, 281

Almagest, 281

Al-Sufi, 47, 149, 179, 189, 221,
224, 225-238, 244, 246, 250,
251, 253, 254, 261, 263, 264,
266-270, 272, 274-278, 285,
287, 289, 290, 293, 298, 300-
302, 304, 307

Altair, 246

Arnpelius, 262
Amphion, 257
Ancient eclipses, 52, 53
Anderson, 120, 277
Andromeda nebula, 193-206,

231

Annals of Ulster, 332
Antares, 60, 179, 310, 311
Anthelm, 300
Antinous, 248
Antlia, 302
Apollo, 257
Apparent diameter of moon,

Apple, 79

" Apples, golden," 258
Apus, 306
Aquarius, 268
Aquila, 246
Aquillus, 220
Ara, 295

Arago, 26, 30, 57, 116, 193, 331
Aratus, 219, 242, 245, 250, 255,

256, 261, 263, 272
Archimedes, 346, 354
Arcturus, 148, 188, 244
Argelander, 29, 227, 229, 230,

240

Argo, 285-288, 305
Argon in sun, 4
Argonauts, 243, 250
Aries, 250
Aristotle, 49, 67
Arrhenius, 4, 8, 22, 45, 66
Ashtoreth, 260

360

INDEX

Astra Borbonia, 4
Astrsea, 263

Astronomy, Laplace on, 44
Astro Theology, 23
Atarid, 232, 233
Atmosphere, height of, 33
Augean stables, 269
Augustus, 262
Auriga, 245
Aurora, 33, 41, 42
Auwers, 206
Axis of Mars, 59

Babilu, 267

Baily, 137, 144

Baker, 183

BaU, Sir Robert, 6, 355

Barnard, Prof., 29, 54, 57, 79,

80, 81, 85, 86, 91, 93, 103,

104, 114, 130, 132, 139, 192,

213, 316, 317, 350
Barnes, 78, 79
Bartlett, 35, 36
Bartschius, 296, 298
Bauschingen, 69, 70
Bayer, 179, 221, 272, 284, 309,

310

Bayeux Tapestry, 105
Becquerel, 8
" Beehive," 259
Beer, 20
Bel, 250
Bellatrix, 253
Benoit, 22
Berenice, 297
Berry, 25
Bessel, 339

Betelgeuse, 179, 222, 264
Bianchini, 21, 22, 77
Biela's comet, 99
Bifornis, 268
Binary stars, 162
Birmingham, 5, 114
" Black body," 3
" Blackness " of sun-spots, C

" Blaze star," 180, 184

Bode, 276

Bohlin, 199, 200

Bond, 85

Bond (Jun.), 74

Book of the Dead, 264, 274

Borelly, 103

Boserup, 28

Boss, 152

Brah<§, Tycho. See Tycho

Brahe

Brauner, 211
Bravais, 42
Bredikhin, 76
Bremiker, 94
Brenner, Leo, 13, 22, 87, 91,

133

Brewster, 356
Brightness of Mercury, 10-12

of nebula, 193
„ of sun, 1, 2, 3

of Venus, 14, 17,

19,31
Bright clouds, 33, 34

„ night, 45

„ stars, 278
Brooks, 118
Brown, 218, 219, 248, 255, 260,

267, 272, 279, 281, 291, 295
Browning, 25
Brugsch, 127
Buddha, 256
Bull, Pope's, 107
" Bull's foot," 253
Buonaparte, 30
Burnham, 160, 165-167, 180,

184, 260, 350, 351
Burns, 130
Buss, 4

Caaba, 125
Cacciatore, 72
Caelum, 302
Callimachus, 297
Callixtus III., 107

INDEX

361

Calvisius, 53
Camelopardalis, 296
Cameron, 18

Campbell, 85, 153, 159, 178
" Canals " on Mars, 61-63
Cancer, 258, 259
Canes Venatici, 296
Canicula, 280
Canis Major, 279

,, Minor, 284
Canopus, 157, 286, 344
Capella, 156, 164, 189, 236,

245, 246

Capricormis, 267, 268
" Capture " of satellites, 58
Carbonic acid, 66
Cassini, 20, 22, 74, 78, 358
Cassiopeia's Chair, 244
Castor, 160, 257
Caswell, 52
Catullus, 297
Caussin, 225
Cecrops, 268
" Celestial Kivers," 308
Celoria, 324, 326
Centaurus, 292, 293
Centre of gravity, 8
Cephalus, 279
Cepheid variables, 187
Ceraski, 2, 176
Cerberus, 243, 257
Ceres, 260
Cerulli, 22, 62
Cetus, 272
Chacornac, 18, 84
Ghamselion, 305
Chamberlin, 194
Chambers, 72
" Charles' Wain," 240
Chinese Annals, 19, 30, 105,

186, 223,267, 330
Childrey, 128
Chiron, 295
Christmann, 281
Chromosphere, sun's, 4
Cicero, 49, 262, 280, 355
Circinus, 307
Clavius, 334

Climate, 45

" Coal Sack," 293, 320

Cobham, 88, 102

Colbert, 175

Colours of stars, 140, 141, 183-

190

Coma Berenices, 297, 298
Comets, number of, 98

tails of, 115, 116
Comet years, 104
Comiers, 99
Comstock, 90, 146
Condamine, 257
Conon, 297

Coon Butte mountain, 120, 121
Cooper, 3
Copeland, 76, 157
Corona, sun's, 1, 334

,, round moon, 35, 36
Corona Australis, 295
Corvinus, 292
Corvus, 292
Cotsworth, 46
Co well, 105
Crabtree, 337
Crater, 291

Craters on moon, 55, 56
Crawford, 348
Crecy, Battle of, 333
Crescent of Venus, 19, 20
Crommelin, 105, 111
Crucifixion, 18
Curtis, 344
Cusps of Venus, 20
Cygnus, (61), 155
Cynocephalus, 222

Dante, 156, 258, 265

Dark shade on moon, 333

D'Arrest, 94

Darwin, Sir George, 158, 319

" David's Chariot," 241

Davis, 155

Dawes, 168

" Dawn proclaimer," 251

INDEX

Delambre, 185

Delauney, 347

Dembowski, 190

Demetrius, 111

Denning, 11, 74, 77, 84, 86, 87,

89, 99, 118, 340
Derham, 21, 23
Deucalion, 268
De Vico, 21, 22
Diamonds in meteorites, 127
Dilkur, 251
Diodorus Siculus, 127
Diogenes Laertius, 41
Diomed, 272
Dione, 89
" Dipper," 241
Doberck, 160
Dollond, 24
Domitian, 334
Donati's comet, 100
Dorado, 304
Dordona, 256
Dorn, 245
Douglass, 81
Dragon, 242
Draper, 75
Drayton, 156
Dreyer, 115
Drifting stars, 152
Dryden, 242
Duncan, 187
Dunlop, 264
Dupret, 83
Dupuis, 245, 252, 257, 258,

259, 266, 267, 268
" Dusky star," 272

" Earthen jar," 247

Earth's attraction on moon,

Earth's motions, 39
„ rotation, 46
„ surface, 32
"Earthshine" on moon, 51,
52, 56, 57

Eastmann, 316
Easton, 323, 324, 325
Eclipses, ancient, 52, 53, 57, 58
„ dark, of moon, 53, 57,
58

Ecliptic, obliquity of, 47
Eddington, 357
Electra, 19
Elster, 39
Emerson, 353
Enceladus, 89
Encke, 113, 116, 240
Ennis, 189

Eratosthenes, 250, 297, 345
Eridanus, 274-278
Eros, 69, 70, 71
Eta Argus, 177, 287
Eudemus, 47
Eudoxus, 218, 219, 223
Euler, 56
Eunomia, 71
Europa, 252

Fabritius, 4, 101

Fabry, 1

Faint stars in telescope, 17G

" False Cross," 156

" Famous stars," 246

Fath, 130, 213

Faye, 100

February, Five Sundays in, 36

Fergani, 189

" Fisher Stars," 256

" Fishes in Andromeda," 249

Fitzgerald, 127

Flammarion, 22, 26, 50, 138,

255, 265, 276
Flamsteed, 348
" Flat earth " theory, 32
Fornalhaut, 271, 309, 310
Fontana, 20
Fontenelle, 357
Forbes, 82, 95, 96
Fornax, 301
Fournier, 87

INDEX

363

Fovea, 284
Freeman, 88
Freret, 222
Frisby, 101
Fritsch, 21
Furner, 163

Gale, 78

Galileo, 3, 4, 80, 82

Galle, 94, 341

Ganymede, 268

Gaseous nebula, spectra of,

195-198,212
Gassendi, 14, 139
Gathman, 118
Gaubil, 99
Gauthier, 103
Gegenschein, 131
Gemini, 257, 258
Geminid variables, 187
Gentil, Le, 338, 339
Gertel, 39

Ghizeh, Pyramids of, 353
Gibbous pbase of Jupiter, 75
Gill, Sir David, 118, 215, 216,

346

Glacial epoch, 42
Gledhill, 76

Globular clusters, 214, 215
Goad, 12
Goatcher, 179
" Golden apples," 258
Golius, 281
Gould, 229, 278, 301, 304, 309,

310, 326

Grant, 82, 96, 345
Gravitation, Law of, 15, 40
Greely, 186
Greisbach, 80
Groombridge 1830, 159
Grubb, Sir Howard, 164
Gruithuisen, 21, 25, 26, 28
Gruson, 127
Guillaume, 331
Guthrie, 25

Habitability of Mars, 63-66
„ of planets, 40
Hadrian, 248
Halbert, 78
Hale, 148, 150
Hall, 15, 131
Halley, 14, 17, 99, 105, 106,

108, 109, 116, 143, 145, 276
Halm, 122
Halo, 35, 36
Hanouman, 284
Hansen, 351
Hansky, 27
Harding, 25, 26, 94
" Harris, Mrs.," 90
Hartwig, 88, 173
Harvests, 104
Heat of sun, 2, 3, 7
Height of atmosphere, 33
Heis, 132, 175, 189, 227, 229,

344

Helium, 4
Hepidanus, 267, 348
Hercules, 243, 259, 268
Herod, 18, 53
Herschel, Miss Caroline, 193,

194, 324, 357
Herschel, Sir John, 112, 177,

190, 207, 209, 210, 215, 289,

314, 346, 353
Herschel, Sir Wm., 3, 24, 80,

112, 114, 115, 116, 171, 178,

179, 190, 324, 325
Hesiod, 17, 220
Hesperus, 256
Hevelius, 99, 116, 221, 29C,

299, 300
Hill, 87, 355

Hind, 19, 30, 54, 105, 111, 180
Hipparchus, 135, 221-223, 226,

250, 278, 281, 293, 329
Hippocrates, 258
Hirst, 333
Holetschak, 108
Homer, 17
Honorat, 84

364

INDEX

Hooke, 74, 128

Horace, 280

Horologium, 303

Horus, 145, 253

Horrebow, 29

Horrocks, 337

Hortensus, Martinus, 139

Hough, 76

Houzeau, 227, 229, 262, 274,

344

Hovedin, Roger de, 53
Hubbard, 100

Huggins, Sir Wm., 91, 148, 180
Humboldt, 30, 82, 83, 124, 128,

134, 154, 157, 342, 352, 357
Hussey, 88

Hyades, 157, 252, 253, 257
Hydra, 288
Hydrus, 303
Hyperion, 88, 90

Ibn al-Aalam, 225

Ibn Alraqqa, 281

Icarus, 284

Indus, 307

Inhabited worlds, 328, 357

Innes, 78, 168

Intra-Mercurial planet, 14, 15,

Invention of telescope, 342
lo, 252
Ions, 27
Iris, 71

Isaiah, 17, 356
Isis, 252, 261, 282, 283
Istar, 260

Jansen, 342
Japetus, 89, 90
Jason, 257, 285
Johnson, Rev. S. J., 19
Jonckheere, 15
Jones, 129

Jordan, 174
Jupiter, chap. viii.

„ gibbous form of, 75

,, and sun, 8

Kalevala, 240

Kapteyn, 314, 316, 321, 322,

326, 357

Kazemerski, 244
Keeler, 86, 215
Kelvin, Lord, 206, 315, 316
Kempf, 174
Kepler, 52, 57, 298, 340, 341,

351

Khayyam, Omar, 127
Kimah, 255
Kimball, 51
Kimta, 255
Kirch, 23, 115
Kirkwood, 6
Kleiber, 123
Klein, 114, 183
Knobel, 238, 263
Konkoly, 183
Koran, 127, 270
Kreusler, 4
Kreutz, 101, 112

Lacaille, 294, 301, 302

Lacerta, 300

Lagrange, 345

La Hire, 20, 21

Lalande, 143, 144, 284

Landerer, 52

Langdon, 25

Langley, Prof., 3

Laplace, 43, 44, 98, 346, 351,

354

Larkin, 65
Lassell, 77, 128
" Last in the River," 275-298
Last year of century, 37

INDEX

365

Lau, 178, 183

Leo, 259

Leo Minor, 298

Lepus, 278, 279

Lernsean marsh, 258

Leverrier, 44, 347, 351

Lewis, 156, 162

Lewis, Sir G. C., 17

Lexell's comet, 98

Libra, 262

Life, possible, in Mars, 63-65

Light of full moon, 1, 51

Lippershey, 342

Littrow, 339

Lockyer, Sir Norman, 144,

147

Lodge, Sir Oliver, 55
Long, 343, 357
Longfellow, 156, 273
Lottin, 42

Lowell, 22, 43, 59, 61, 64, 88
Lucifer, 17
Lucretius, 320
" Luminous clouds," 33, 34
Lunar craters, 55, 56

„ " mansions," 251

„ mountains, 58

„ theory, 56
Lunt, 179
Lupus, 294
Lyman, 25
Lynn, 37, 38, 96, 106, 179, 243,

244, 310
Lynx, 296
Lyra, 243, 244, 266

Maclear, 77
Madler, 20, 22
Msestlin, 341
Magi, star of, 1, 18, 145
Magnitudes, star, 311
Maia, 19, 256
Mairan, 357
" Manger," 259

Manilius, 250, 259, 272

Marius, Simon, 82, 83, 231

Markree Castle, 3

Marmol, 76

Mars, chap. vi. ; axis of 59 ;
red colour of, 60; water
vapour in, 60 ; clouds in, 61 ;
" canals " in, 61

Martial, 17

Mascari, 22

Ma-tuan-lin, 186, 267

Mayer, 24

May transits of Mercury, 15

Maxwell, Clerk, 86

McHarg, 16

McKay, 286

Medusa, 244

Mee, 88

Melotte, 82

Mendelief, 212

Mensa, 304

Mercury, chap, ii., 258

Merrill, 121

Messier, 114

Meteoric stones, 119

Meteors, 33

Metius, 342

Microscopium, 302

Milky Way, 320, 323, 325, 326,
328

Milton, 263

Mimas, 88, 89

Minor planets, chap. vii.

Mira Ceti, 178, 186, 272, 273

Mitchell, 4

Mithridates, 111

Mitra, 145

Molyneux, 80

Monck, 156, 181

Monoceros, 298

Montanari, 170, 171

Montigny, 34

Moon, light of, 1, 51

,, as seen through a tele-
scope, 50

l< Moon maiden," 52

Moon mountains, 58

Morehouse, 103, 110

366

INDEX

Motions of stars in line of

sight, 141, 142
Moulton, 133, 318
Mountains, lunar, 58
Miiller, 174
Musca, 305
Mycerinus, Pyramid of, 353

Nasmyth, 11

Nath, 253

Nautical Almanac, 349

Nebula in Andromeda, 198-

206, 231
Nebulae, gaseous, 195-198,

212, 213

Nebulae, spiral, 213
Nebular hypothesis, 354
Nemselian lion, 259
Nemseus, 259
Neon in sun, 4
Nepthys, 271
Neptune, 341
Newcomb, 13, 15, 33, 50, 65,

70, 129, 130, 153, 191, 203,

282, 339, 347, 349, 350, 355
Newton, 15, 351
Nicephorus, 127
Nicholls, 148, 154
Nineveh tablets, 17
Noble, 25
Norma, 302

Novas, 180-182, 265, 267, 343
Nova Persei, 190
November transits of Mercury,

15
Number of nebulae, 191

„ of stars, 135, 136, 236,

237
Number of variable stars, 182,

183

Obliquity of ecliptic, 47
Occultations, 14, 15, 54, 67, 80,
84, 85, 259, 340, 341

Octans, 303
Odling, 122
Oeltzen, 72
Gibers, 104, 124
Old, 340

Orion, 49, 146, 273, 274
Osiris, 145, 259, 261, 283
" Ostriches," 266
Otawa, 240

Ovid, 242, 250, 255, 265, 288,
291, 322

Palisa, 71

Palmer, 182

Parker, 19

Parkhurst, 174

Paschen, 2

Pastorff, 25

Pavo, 307

Payne, 139

Pearson, 77

Peary, 119

Peck, 176

Pegasus, 248

Pelion, 282

Peritheus, 258

Perrine, 15, 76, 191, 192, 214

Perrotin, 351

Perseus, 244

Petosiris, 222

Philostratus, 334

Phlegon, 332

Phcebe, 90

Phomix, 301

Phosphorus, 17

Photographic nebula, 192

Pickering, E. C., 125, 140, 144,

177
Pickering, W. H., 1, 12, 51, 61,

95, 102
Pictor, 304
Pierce, 228

" Pilgrim Star," 180, 185, 186
Pingre, 54
Pinzon, 294

INDEX

367

Pisces, 271

Piscis Australis, 295, 296

Planetary nebulae, 213

Platina, 107

Pleiades, 19, 52, 137, 154, 157,

235, 254-257
Pliny, 17, 265, 280
Plummer, W. E., 180
Plurality of worlds, 328, 356,

357

Pococke, 271
Pogson, 317
Polarization of moon's surface,

Polarization on Mars, 61
Pole of cold, 33

„ star, 138, 239, 240
Pollux, 257
Polydectus, 244
Poor, 15 (footnote)
Poynting, 130
Prsesape, 259
Prince, 25
Proclus, 221
Proctor, 7, 49, 59, 123, 285,

308, 323, 352

Procyon, 156, 157, 236, 284
Ptolemy, 189, 221-223, 224,

227, 230, 231, 234, 238, 244,

252, 253, 260, 263, 264, 267,

269, 275, 278, 281, 284, 293,

302, 330
Pyramid, Great, 46, 47, 308,

353
Pytheas, 46

Quadruple system, 168
Quenisset, 21, 133

Rabourdin, 103
Radium, 7, 8, 3*

Rahu, 93

Rama, 284, 340

Rational Almanac, 46

" Red Bird," 290

Red star, 279, 292

Regulus, 30, 156, 235, 236, 260,
310, 340

Remote galaxies, 193, 204,
205

Reticulum, 304

Rhea, 89

Rheita, De, 144

Riccioli, 189

Ricco, 32

Rigel, 156, 157, 222

Rigge, 107

Ring nebula in Lyra, 211

Rings of Saturn, 85

Rishis, 240

Ritter, 76, 147

" Rivers, celestial," 308

Roberts, Dr. A. W., 172, 173

Roberts, Dr. I., 95, 154, 200,

201, 203, 317
Roberts, C., 84
Robigalia, 280
Robinson, 342, 357
Rcsdeckcer, 28
Rogovsky, 42, 43, 44, 75
Rosse, Lord, 76
Roszel, 70

Rotation of Mercury, 16
„ of Uranus, 91
,, of Venus, 22
Rubaiyat, 127
Rudaux, 80, 89
Russell, H. C., 21
Russell, H. N., 146
Russell, J. C., 333
Rutherford, 38

Sadler, 78, 299
Safarik, 24, 25
Sagittarius, 265-267

368

INDEX

Sahu, 274
Santini, 357

Satellite, eighth, of Jupiter, 82
„ possible lunar, 54

of Venus, 28, 29
Sawyer, 186
Sayce, 218, 261
Scaliger, 299
Schaeberle, 93
Schaer, 88

Schemer, 4, 150, 188, 195
Scheuter, 30
Schiaparelli, 22, 326
Schjellerup, 226, 228, 230, 231,

264, 277, 281, 340
Schlesinger, 183
Schbnfeld, 287
Schiraz, 47

Schmidt, 51, 188, 220, 271
Scholl, 79
Schroter, 13, 20, 21, 22, 24, 26,

Schuster, 2, 148, 149, 150
Schwabe, 5
Scorpio, 263-265
Sculptor, 301
Scutum, 299
Searle, 132
" Secondary light " of Venus,

23-28
See, Dr., 12, 13, 33, 58, 96, 161,

164, 165, 210, 211, 281, 282,

354

Seeliger, 181, 206
Seneca, 218, 220
Serapis, 145
Sestini, 190

" Seven Perfect Ones," 256
Sextans, 298
Shaler, 48
Sharpe, 357
Shelley, 356
Shicor, 274
" Ship," 285
" Sickle," 259
Signalling to Mars, 65
Sihor, 280
Silkit, 264

Silvestria, 124

Simeon of Durham, 53

Simonides, 255

" Singing Maidens," 256

Sirius, 138, 156, 157, 160, 163,
236, 274, 280, 282, 283

Slipher, 60, 87, 161, 178

Smart, 109

Smyth, Admiral, 12, 72, 77,
107, 136, 140, 145, 170, 176,
190, 194, 253, 259, 351

Snyder, Carl, 8, 345

Sobieski, 299

Sola, Comas, 81, 87

Somerville, Mrs., 357

Sothis, 286

Southern Cross, 293, 344

Spectra of double stars, 162

Spectrum of gaseous nebulic,
195-198, 212

Spectrum of sun's chromo-
sphere, 4

Spencer, Herbert, 193

Sphinx, 261

Spica, 156, 236

Spiral nebulae, 213

Star magnitudes, 311

" Star of Bethlehem," 17, 18

Stars in daytime, 158

Stebbins, 51

Stockwell, 18, 331

" Stones from heaven," 125,
126

Stoney, 133

Strabo, 127

Stratonoff, 151, 320, 321

Stromgen, 88

Strutt, 7

Struve, 113, 240

Struyck, 54

Succulse, 253

Suhail, 283, 286

Sun darkenings, 5, 335, 336

Sun's heat, 7

Sunlight, 1, 2

Sun-spots, 5, 6

Swift, 102

Sydera Austricea, 5

INDEX

369

Tacchini, 22

Tamerlane, 238

Tammuz, 261

Tarde, 4

Taurus, 251

Taylor, 40

T Coronse, 184

Tebbutt, 183, 278

Telescopium, 302

Temporary stars, 180-182, 265,

267, 343
Tennyson, 40
Terby, 88
Tethys, 89
Thales, 357
Tb,ebes, 271
Themis, 88-90
Theogirus, 279
Theon, 245
Theseus, 257
Thome, 101
Thucydides, 331
Tibertinus, 281
Tibullus, 282
Tides, 40
Timocharis, 340
Tin, 179

Titan, 85, 88, 89
Titanium, 179
Toucan, 308
Transits of Mercury, 14, 15

of Venus, 337, 338,

339
Triangulum, 271

„ Australis, 306
Trio, 220
Triptolemus, 257
Triton, 93

Trouvelot, 21, 22, 78, 211
Tumlirz, 46
Turrinus, 220
Tycho Brahe, 10, 30, 99, 145,

179, 298
Typhon, 263, 272

Ulugh Beigh, 238, 276, 278

Underwood, 85

Uranus, chap. x. ; spectrum

of, 91, 92
Urda, 71

Valz, 72

" Vanishing star," 59

Varvadjah, 236

Vega, 148, 156, 244

Vencontre, 220

Venus, chap. iii. ; apparent
motion of, 28 ; supposed
satellite of, 28, 29 ; transit
of, 337-339

Veronica, S, 145

Vesta, 70

Virgil, 17, 218, 242, 262, 309

Virgo, 260

Vogel, 180

Vogt, 122

Volans, 304

Voltaire, 15

Von Hahn, 24

Vulpecula, 300

Wallace, Dr., 212, 357

Wallis, 80

Ward, 88

Wargentin, 178

Watson, 339

Webb, 24, 25, 77, 190, 286

Weber, 183

Weinhand, 122

Wendell, 71, 103, 109

Werchojansk, 33

White spots on Jupiter's

satellites, 81

White spots on Venus, 21
Whitmell, 50, 86
Wiggins, 333

2 B

370

INDEX

Wilczyniski, 195

Williams, Stanley, 22. 277,

302

Wilsing, 155
Wilson, H. C., 137, 139
Wilson, Dr. W. E., 3, 148
Winnecke, 26, 188
Winterhalter, 351
Wolf, Dr. Max, 71, 72, 191,

211, Note p. 537
Wrangel, 240

Young, Prof., 4, 7, 9
Young, Miss Anne S., 79
Yunis, Ibn, 30

Zach, 331
Zenophon, 127
Zethas, 257
Zollner, 27

THE END

FEINTED BT WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BKCCLES.

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